ENGINEERING    OF    TO-DAY 


THE  "EYE  "  OF  THE  SUBMARINE  BOAT 

When  moving  under  water  the  "man  at  the  wheel"  sees  his  way  by  means  of  the 
periscope,  which  projects  above  the  surface,  but  is  so  small  that  it  cannot  itself  be  seen. 
At  the  top  of  the  tube  is  an  artificial  eye,  and  what  that  eye  sees  is  reflected  down  the  tube 
and  into  the  real  eyes  of  the  man  below. 


ENGINEERING    OF 
TO-DAY 

A    POPULAR   ACCOUNT    OF    THE   PRESENT 

STATE    OF  THE    SCIENCE,    WITH  MANY 

INTERESTING  EXAMPLES,  DESCRIBED 

IN  NON-TECHNICAL  LANGUAGE 


By 
THOMAS  W.    CORBIN 


With  39  Illustrations  fcf  Diagrams 


PHILADELPHIA 
J.   B.    LIPPINCOTT    COMPANY 

LONDON:  SEELEY  AND  CO.  LIMITED 


PREFACE 

ENGINEERING  is  now  recognised  as  one  of  the  sciences, 
and  therefore  naturally  finds  its  place  in  a  series  of 
volumes  dealing  with  the  Science  of  To-day.  It  is 
really  the  science  of  applying  the  older  sciences  to 
the  ordinary  affairs  of  mankind.  The  chemist  investi- 
gates the  causes  of  the  explosion  of  gas  ;  the  engineer 
makes  the  explosions  drive  engines.  The  geologist 
studies  the  structure  of  the  earth's  crust  ;  the  engineer 
makes  use  of  this  acquired  knowledge  in  obtaining  a 
water  supply.  The  mineralogist  examines  the  pro- 
perties of  earths  and  ores,  and  through  his  researches 
the  engineer  is  enabled  to  devise  a  new  method  of 
building. 

Engineering  is  so  closely  connected  with  the  con- 
cerns of  daily  life  that  it  cannot  fail  to  interest  the 
general  reader  if  presented  to  him  in  a  way  that  he 
can  readily  understand,  free  from  the  technical  terms 
which  are  unintelligible  to  him.  I  have  attempted 
this  in  the  present  volume,  and  out  of  the  many  topics 
well  worthy  of  discussion,  I  have  selected  those  which 
I  believe  to  be  of  most  general  interest,  and  those 
which  are  most  typical  of  the  problems  with  which 
the  engineer  has  to  deal.  I  have  not  written  for  the 
professional  reader,  to  whom  many  of  my  descriptions 
would  necessarily  appear  inadequate  and  incomplete. 

The  illustrations  in  the  text  are,  in  most  cases,  not 
exact  drawings,  but  diagrams  intended  to  make  the 
reader  understand  with  the  least  possible  trouble  the 
main  features  of  the  things  represented. 

ix 

222475 


Preface 

Engineering  is  essentially  a  modern  science.  As 
we  know  it  now  it  is  not  much  more  than  a  century 
old,  and  the  rapidity  of  its  progress  seems  to  be 
increasing  as  time  goes  on.  It  already  does  for  us 
many  things  which  our  immediate  ancestors  had  to 
do  for  themselves,  and  what  it  holds  in  store  for  us 
and  our  children  it  were  vain  to  conjecture.  There 
are,  however,  certain  guiding  principles  which  underlie 
the  latest  as  well  as  the  earliest  inventions,  and  I  have 
tried  to  make  these  so  clear  that  the  reader  may  find 
in  the  following  pages  not  merely  a  review  of  the  past, 
but  a  key  to  the  meaning  of  new  developments. 

My  sincere  thanks  are  due  to  those  who  have  kindly 
supplied  the  photographs  from  which  many  of  our 
illustrations  are  taken,  and  to 'several  friends  who,  being 
specialists  in  certain  departments,  have  perused  and  criti- 
cised those  passages  of  my  MS.  which  relate  to  their 
particular  subjects.  I  wish  also  to  acknowledge  my  in- 
debtedness to  Engineering^  the  invaluable  journal  which 
is  studied  by  every  one  who  wishes  to  keep  in  touch 
with  the  various  activities  of  his  profession. 

T.  W.  C. 

WESTMINSTER,  July  1910. 


CONTENTS 


CHAPTER   I 

PAGE 

THE  ENGINEER  AND  THE  PUBLIC 17 


CHAPTER  II 
SOURCES  OF  POWER:  THE  STEAM-ENGINE      ....      24 

CHAPTER   III 
SOURCES  OF  POWER  :  THE  GAS-ENGINE  .       .       .     *  .       -45 

CHAPTER   IV 
SOURCES  OF  POWER  :  RUNNING  WATER 61 

CHAPTER  V 
How  POWER  is  CARRIED 74 

CHAPTER  VI 

THE  ENGINEER'S  MATERIALS  :  IRON  AND  STEEL  ...      88 

CHAPTER  VII 

MORE  MATERIALS 101 

xi 


Contents 

CHAPTER   VIII 


PAGE 

THE  ENGINEER'S  TOOLS 108 


CHAPTER  IX 
BRIDGES .       .     'V      .       .119 

CHAPTER  X 
IRON  AND  STEEL  SHIPS 137 

CHAPTER  XI 
THE  BUILDING  OF  SHIPS  .       .       .       .       .      .       v     .    147 

CHAPTER  XII 
CURIOUS  SHIPS 163 

CHAPTER   XIII 
How  BIG  GUNS  ARE  MADE 173 

CHAPTER   XIV 
WAR  VESSELS 180 

CHAPTER  XV 
SUBMARINE  DIVING 194 

CHAPTER  XVI 

WATER-SUPPLY ,204 

xii 


Contents 

CHAPTER   XVII 


PAGE 

ELECTRIC  TRACTION 217 


CHAPTER   XVIII 

THE  IRON  HORSE 235 

CHAPTER  XIX 
How  RAILWAYS  ARE  WORKED 249 

CHAPTER  XX 
RAILWAY-SIGNALLING  MACHINERY 264 

CHAPTER   XXI 
THE  MANUFACTURE  OF  GAS 276 

CHAPTER   XXII 
ELECTRIC  LIGHTING  AND  HEATING        .....    289 

CHAPTER  XXIII 
MEASURING  TO  A  HAIR'S  BREADTH 303 

CHAPTER   XXIV 
LIFTING  AND  CONVEYING  MACHINERY 318 

CHAPTER   XXV 

PROTECTION  FROM  FIRE 327 

xiii 


Contents 

CHAPTER   XXVI 


PAGE 


THE  CONQUEST  OF  THE  AIR 335 

CHAPTER   XXVII 

A  MISCELLANEOUS  CHAPTER ,       .  350 

CHAPTER  XXVIII 

ENGINEERING  OF  TO-MORROW 355 

INDEX 365 


xiv 


LIST    OF    ILLUSTRATIONS 

THE  "EYE"  OF  THE  SUBMARINE  BOAT  .          Frontispiece 

PAGE 

GIGANTIC  CRANES  USED  IN  SHIPBUILDING       ...       20 

THE  SOUL  OF  THE  STEAM-ENGINE 26 

AN  ELECTRO-MAGNET  FOR  LIFTING  PIG-!RON         .        .       76 

ELECTRICITY  AT  THE  COAL-MINE 80 

BLAST  FURNACE  FOR  SMELTING  IRON     ....      90 

A  MECHANICAL  HAND  AND  ARM 98 

A  PNEUMATIC  HAMMER  AND  CHISEL      .        .        .         .114 

THE    "TRANSPORTER"    BRIDGE    AT    NEWPORT,    SOUTH 

WALES      .        .        .         .         .        .        .        .         .120 

A  yo-ToN  BRIDGE  TAKING  A  RIVER  TRIP      .        .        .128 
SURVEYING  UNDER  DIFFICULTIES    .        .        .        .         .132 

HALF  A  SHIP 160 

CASTING  SHELLS  AT  WOOLWICH  ARSENAL       .        .        .176 

THE  "MINAS  GERAES" 182 

THE  FASTEST  SHIP  IN  THE  WORLD        .        .        .        .188 

A  LIFE-SAVING  HELMET  AND  JACKET     .        .        .        .192 

xv 


PAGE 


List  of  Illustrations 

INSIDE  A  DIVING-BELL    .  ...     198 

WELDING  THE  JOINTS  IN  TRAMWAY-RAILS       .        .        .228 
THE  INTERIOR  OF  A  SIGNAL  CABIN        .  .        .272 

A  "TITAN"  CRANE •     320 

A  "  GOLIATH  "  CRANE J.    322 

Two  TRANSPORTERS  .  •    '324 

AN  AERIAL  ROPEWAY      .        .  .        .  •     32^ 

A  "  HYDROPLANE  " 34^ 

A  "SKIMMER"  .  •     34^ 


xvi 


ENGINEERING   OF   TO-DAY 

CHAPTER  I 

THE  ENGINEER  AND  THE  PUBLIC 

THE  engineer  is  a  much-abused  man. 

One  of  the  greatest  of  English  writers  and  thinkers 
argues  that  his  countrymen  are  not  a  great  nation 
because  they  have  "  turned  every  quiet  valley  into 
a  highway  of  rushing  fire,"  a  gibe  at  one  of  the 
greatest  achievements  of  engineering  ;  and  there  are 
thousands  of  less  eminent  people  than  John  Ruskin 
who,  in  less  eloquent  language,  denounce  the  engineer 
as  a  spoiler  of  natural  beauty,  a  pure  utilitarian  who 
gives  us  smoke  for  pure  air,  grime  instead  of  verdure, 
and  straight  hard  lines  in  place  of  the  soft  lines  and 
graceful  curves  of  nature. 

Yet  the  people  who  speak  thus  do  not  refuse  to 
go  by  train  ;  they  are  not  content  with  candles,  but 
must  have  gas  or  electric  light  ;  if  they  have  to  cross 
the  ocean  they  do  not  seek  for  an  old  wooden  sailing- 
ship,  but  go  by  the  latest  and  fastest  steel  vessel 
with  the  most  modern  engines ;  they  do  not  draw 
water  from  an  old  (and  probably  contaminated)  well, 
but  use  the  pure  water  which  some  maligned  engineers 
have  brought  from  distant  hills,  and  delivered,  clean 
and  pure,  into  their  houses.  In  short,  while  abusing 

17  B 


,  ,.  The  Engineer  and  the   Public 

'the  '  engineer '  they  are  glad  to  take  advantage  of 
his  work. 

The  truth  is  that  the  engineer  is  like  the  doctor — 
a  necessary  evil,  perhaps,  but  necessary  all  the  same  ; 
only  the  public  do  not  do  the  same  justice  to  the 
engineer  that  they  do  to  the  doctor.  A  man  with 
one  arm  is  looked  upon  as  a  monument  to  the  bene- 
ficent skill  of  the  surgeon  ;  but  a  railway  or  an  aque- 
duct, still  more  a  factory  chimney,  is  regarded  simply 
as  a  blot  on  the  landscape. 

Yet  the  engineer  does  not  build  his  railway  or  his 
chimney  for  the  fun  of  the  thing,  any  more  than  does 
the  doctor  amputate  a  man's  arm.  Both  do  their  work 
because  it  needs  to  be  done.  The  medical  man  oper- 
ates because  the  safety  of  his  patient  depends  upon  it, 
and  the  engineer  builds  and  constructs  because  the 
needs  of  the  community  call  upon  him  to  do  so. 

There  are  remote  districts  in  India  which,  in  the 
event  of  a  failure  of  the  harvest  through  drought,  suffer 
all  the  horrors  of  famine.  There  is  grain  in  existence 
in  plenty,  but  one  of  the  great  difficulties  is  to  get 
it  transported  into  the  famine-stricken  districts.  More 
railways  would  go  far  to  prevent  these  distressing 
periods. 

Indeed,  without  the  railways  and  steamships  of  the 
present  day  there  would  be  some  parts  of  Europe  in  a 
chronic  state  bordering  on  famine,  and  it  almost  seems 
as  if  the  railway  and  the  steamship  had  been  brought 
into  existence  by  an  over-ruling  power  just  at  the 
"  psychological  moment "  when  they  became  necessary 
to  carry  food-stuffs  to  the  densely  populated  areas. 

Then,  apart  from  the  carrying  of  food,  who  can  esti- 
mate the  sum  of  human  happiness  which  is  entirely 
due  to  the  modern  facilities  for  travel  ?  There  are  the 
visits  of  children  to  the  old  folks  at  home ;  the 
pleasant  trips  into  new  and  strange  lands  ;  the  ming- 

18 


The  Engineer  and  the  Public 

ling  together  of  the  nations — the  last  of  which  is  pro- 
bably the  most  potent  of  all  the  influences  tending  to 
bring  about  that  era  of  universal  peace  and  friendship 
among  the  peoples  of  the  earth,  which  men  have  hoped 
for  for  centuries,  and  which  now  really  seems  to  be  ap- 
proaching. 

And  facilities  for  travel  and  transport  are  but  one 
branch  of  the  engineer's  work.  There  are  others  in 
which  his  efforts  are  almost  as  beneficent.  Is  it  too 
much,  then,  to  claim  that  the  benefits  conferred  upon 
mankind  by  the  labours  of  the  engineer  far  outweigh 
an  occasional  spoiling  of  a  landscape  or  the  shutting 
out  of  a  favourite  view  ? 

Then  there  are  people  who  look  for  infallibility  in 
an  engineer,  and,  failing  to  find  it,  write  down  him  and 
all  his  kind  as  "  frauds."  A  business  man,  for  example, 
has  clerks  who  keep  his  accounts,  involving  thousands 
of  transactions  and  hundreds  of  thousands  of  pounds, 
and  who  make  them  balance  at  the  end  of  the  year 
to  a  penny.  He  therefore  expects  the  same  freedom 
from  error  in  an  engineer,  forgetting  that  copying 
figures  from  one  book  to  another  and  adding  them 
up  is  a  very  different  matter  from  wrestling  with  the 
forces  of  nature.  In  an  engineering  undertaking  of 
any  magnitude  the  questions  involved  are  so  complex 
that,  in  Mr.  Gladstone's  historic  phrase,  it  "  passes  the 
wit  of  man "  to  anticipate  and  provide  for  them  all. 
Consequently  things  are  bound  to  "  crop  up "  un- 
expectedly as  the  work  proceeds,  and  those  concerned 
in  the  enterprise  then  blame  the  engineer  for  not 
having  thought  of  them  earlier,  a  state  of  things  which 
is  constantly  arising,  particularly  in  municipal  under- 
takings. 

Another  reason  why  the  public  are  apt  to  undervalue 
the  skill  of  the  engineer  is  because  they  do  not  realise 
the  great  gulf  between  theory  and  practice.  A  scheme 

19 


The  Engineer  and  the  Public 

may  be  theoretically  perfect ;  but  since  there  is  no  such 
thing  as  a  perfect  material,  and  as  the  perfect  workman 
has  yet  to  be  discovered,  it  may,  in  practice,  be  quite  the 
reverse.  Now  the  engineer  has  learnt  from  experience 
that  allowance  must  be  made  for  these  practical  imper- 
fections, while  the  layman  has  not. 

I  know  of  an  instance  which  illustrates  this.  A 
certain  firm  built  a  large  furnace  of  brickwork,  held 
together  by  a  steel  frame.  After  a  short  time  the 
steelwork  gave  way,  and  the  structure  fell  to  pieces. 
The  firm  happened  to  be  at  that  moment  without  a 
technical  adviser,  so  the  commercial  men  attempted 
to  deal  with  the  matter  themselves.  They  reasoned 
thus.  The  design  is  the  same  as  other  furnaces,  which 
are  standing  well  ;  the  bricks  are  the  same,  and  the 
same  men  laid  them  ;  everything  is  exactly  the  same 
in  this  furnace  as  in  the  others,  except  the  steelwork, 
which  was  supplied  by  a  different  maker  ;  therefore 
it  must  be  the  fault  of  the  steel.  That  sounds,  on  the 
face  of  it,  and  undoubtedly  is  theoretically,  a  perfectly 
sound  proposition,  as  conclusive,  apparently,  as  a  pro- 
position in  Euclid,  and  on  the  strength  of  it  the  firm 
claimed  damages  against  the  steelmaker ;  but  any 
engineer  would  know  in  a  moment  that  it  is  as  weak 
as  water.  For  no  one  can  say  that  two  such  structures, 
even  if  built  to  the  same  drawings,  of  similar  materials, 
and  by  the  same  men,  will  be  exactly  alike.  A  few 
defective  bricks,  a  pailful  of  badly  mixed  concrete,  a 
difference  in  the  weather  when  the  work  was  done,  an 
unknown  fault  in  the  ground  under  the  foundations, 
any  of  these  things  may  make  a  difference. 

In  this  case  an  arbitrator  was  ultimately  called  in 
to  decide  where  the  responsibility  lay.  He  examined 
the  broken  piece  of  steel  and  found  no  flaw.  He 
found,  however,  signs  that  it  had  been  subjected  to 
intense  heat,  and  further  minute  investigation  revealed 

20 


g     8E 

5    -I 


The  Engineer  and  the  Public 

the  fact  that  the  foundations  had  settled  unequally, 
cracked  the  brickwork,  and  laid  the  steel  open  to  the 
full  heat  of  the  furnace.  That,  becoming  softened 
by  the  heat,  gave  way  and  the  whole  affair  collapsed. 
The  apparently  perfect  proposition,  as  to  the  responsi- 
bility, likewise  collapsed  when  the  matter  was  thus  sub- 
jected to  thorough  examination. 

The  theoretical  perfection  which  some  people  expect 
to  be  attained  with  the  imperfect  materials  and  methods 
which  alone  are  available  in  this  world,  has  been  cleverly 
satirised  by  Oliver  Wendell  Holmes  in  his  humorous 
little  poem  "The  Wonderful  One-Hoss  Shay."  In  this 
he  tells  of  a  man  who  observed  that  carts  always  broke 
down  and  never  wore  out,  which  he  attributed,  rightly, 
to  the  fact  that  some  parts  are  relatively  weaker  than 
others.  He  decided,  therefore,  to  build  himself  a 
carriage  in  "a  perfectly  logical  way,"  in  which  every 
part  should  be  of  exactly  the  correct  relative  strength. 
This  marvellous  vehicle  ran  for  one  hundred  years 
exactly  without  showing  any  sign  of  wear,  and  then, 
in  a  moment,  every  part  broke  at  once  and  the  car- 
nage fell  into  small  pieces  "as  if  it  had  been  ground 
in  a  mill."  It  only  needs  to  be  related  to  be  laughed 
at,  yet  it  is  simply  the  views  of  many  people  in  regard 
to  engineering  matters  carried  to  their  logical  con- 
clusion. 

It  will  be  noticed  that,  above,  I  have  used  the  con- 
ventional conception  of  theory  as  opposed  to  practice, 
but  in  reality  there  is  no  opposition  between  the  two. 
We  often  say  that  a  thing  is  perfect  in  theory  but 
will  not  work  in  practice,  but  that  is  only  because  in 
forming  our  theory  we  have  omitted  to  take  into  ac- 
count some  factor  the  presence  of  which  makes  our 
theory  a  false  one.  If  we  do  not  realise  this,  we  are 
apt  to  discredit  theory  and  fall  back  upon  methods 
usually  described  by  the  term  "  rule  of  thumb,"  whereas 

21 


The  Engineer  and  the  Public 

the  real  lesson  to  be  learnt  from  this  apparent  conflict 
between  theory  and  practice  is  that  by  study  and  in- 
vestigation we  should  seek  to  make  our  theories  more 
perfect. 

Nowadays  there  are  few  people  who  do  not  come 
more  or  less  into  touch  with  engineering  matters. 
Business  men,  from  the  directors  of  great  companies 
to  the  owners  of  very  humble  shops,  must  needs,  if  they 
wish  to  succeed,  accept  the  engineer's  help. 

The  up-to-date  grocer  has  his  electrical  coffee-roaster, 
the  baker  his  mechanical  dough-mixer,  while  the  laun- 
dryman  does  nearly  everything  by  machinery,  and 
these  are  but  a  few  of  the  trades  which  the  engineer 
helps  ;  and  there  is  not  one  of  them  but  will  be  the 
better  off  for  a  little  more  intimate  knowledge  of 
engineering  matters,  for  without  it  they  are  apt  to  fall 
into  curious  blunders. 

I  heard  of  an  amusing  case  the  other  day.  A  firm 
starting  a  new  factory  purchased  a  steam-engine  and 
boiler  of  which  they  were  very  proud,  but  they  unfor- 
tunately entrusted  its  care  to  a  rather  careless  attend- 
ant. This  man  allowed  the  water  in  the  boiler  to  get 
too  low,  with  the  result  that  the  "  fusible  plug  "  melted 
and  put  the  fire  out.  This  "  fusible  plug,"  which  will 
be  explained  more  fully  in  a  later  chapter,  is  a  safety 
device,  and  is  intended  to  melt  under  these  circumstances, 
in  order  to  avoid  more  serious  disaster.  The  plug  was 
replaced;  but  a  few  weeks  later,  again  through  careless- 
ness, the  same  thing  occurred  again,  whereupon  the  firm 
sent  a  sharp  letter  to  the  makers  angrily  demanding 
to  know  what  they  meant  by  supplying  "  fusible  plugs  " 
which  burnt  out  so  often.  They  did  not  know  it,  but 
they  might  just  as  reasonably  have  complained  of  their 
boiler  being  fitted  with  a  safety-valve,  on  the  ground 
that  it  let  a  certain  amount  of  steam  out. 

Then  there  is  a  large  section  of  the  public  who  are  by 

22 


The  Engineer  and  the  Public 

nature  interested  in  engineering.  Many  of  them  feel 
that  they  ought  to  have  been  engineers,  only  an  unkind 
fate,  such  as  a  paternal  business,  decreed  otherwise. 
They  feel  attracted  by  any  example  of  engineering  that 
they  may  meet  with  ;  but  unfortunately  they  are  often 
unable,  through  insufficient  knowledge,  to  understand 
what  they  see.  They  are  like  amateurs  whom  I  have 
observed  at  engineering  exhibitions,  wandering  round 
endeavouring  in  vain  to  understand  the  exhibits,  and 
delighted  beyond  measure  if  some  friendly  engineer 
will  take  the  trouble  to  initiate  them  into  the  mysteries. 
It  is  to  such  that  this  book  is  particularly  addressed. 
The  various  branches  of  the  engineer's  work  are  here 
exhibited  not  with  descriptions  merely,  but  explana- 
tions, where  possible,  of  the  underlying  principles,  the 
methods  of  design,  and  the  reasons  why  different 
problems  are  attacked  in  different  ways.  These  will 
help  the  amateur  engineer  to  understand  more  easily 
what  he  sees,  and  enter  more  intelligently  into  the 
questions  with  which  his  professional  brother  is  engaged. 


CHAPTER   II 

SOURCES   OF  POWER 
THE    STEAM-ENGINE 

IT  will  be  evident  to  every  one  that,  without  some 
means  of  generating  power,  most  of  the  industries  of 
modern  life  would  be  impossible. 

The  force  which  man  is  able  to  exert  by  the  exercise 
of  his  own  muscles  is  only  trifling  ;  but,  fortunately  for 
him,  the  mental  powers  with  which  he  is  endowed 
enable  him  to  turn  to  his  own  use  the  vast  stores  of 
energy  which  are  locked  up  in  nature.  For  many 
centuries  the  force  of  the  wind  has  been  utilised,  while 
the  idea  of  a  wheel  turned  by  the  power  of  falling 
water  is  of  still  greater  antiquity,  but  the  greatest  of 
all  the  natural  sources  of  power,  Heat,  has  only  been 
tapped  in  comparatively  modern  times. 

Ages  ago,  when  parts  of  the  earth  now  known  as 
Britain  and  America  were  covered  with  vast  tropical 
forests,  the  heat  of  the  sun  enabled  the  vegetation  to 
perform  a  certain  chemical  process.  The  carbonic- 
acid  gas  in  the  air  was  separated  into  the  two  elements 
of  which  it  is  composed.  One  of  these,  the  carbon, 
was  built  into  the  structure  of  the  trees  and  plants, 
while  the  other,  the  oxygen,  was  liberated  into  the 
atmosphere. 

Now  none  of  the  energy  in  the  universe  is  ever  lost. 
It  may  be  changed  from  one  form  into  another,  as  when 
the  energy  expended  in  rubbing  out  a  pencil-mark  is 

24 


Sources  of  Power 

converted  into  heat  which  can  be  felt  in  the  india- 
rubber,  but  it  is  still  in  existence.  So  the  energy  of 
the  sun  which  was  expended  all  those  thousands  of 
years  ago  is  still  in  existence  in  the  coal  which  was 
ultimately  formed  out  of  that  tropical  vegetation.  The 
coal  has  only  to  be  dug  up  and  subjected  to  a  certain 
amount  of  heat  in  the  presence  of  oxygen  for  the  re- 
verse process  to  be  set  up.  The  carbon  and  oxygen 
once  more  combine  together  into  carbonic  acid,  and  the 
heat  which  was  used  up  in  the  dim  past  in  separating 
them  is  given  back.  It  is  this  which  accounts  for  the 
heat  of  a  coal  fire. 

We  are  thus  in  possession  of  enormous  stores  of 
energy  which  can,  if  proper  means  are  employed,  be 
converted  into  mechanical  motion  and  used  for  driving 
machinery  of  all  kinds,  and  one  of  the  most  important 
functions  of  the  engineer  is  to  devise  the  most  efficient 
way  of  doing  this. 

The  machines  which  have  been  invented  for  effecting 
the  conversion  of  heat  into  power  fall  naturally  into 
two  classes,  steam-engines  and  gas-engines.  Of  these 
the  former  is  the  older  and  the  most  largely  used,  so 
we  will  give  that  our  first  consideration. 

When  a  substance  is  heated  it  almost  invariably 
expands  with  great  force.  I  heard  only  a  short  time 
ago  of  an  incident  which  illustrates  this.  One  of  the 
engineers  employed  in  the  building  of  the  Forth  Bridge 
told  me  how  the  bridge  used  to  bend  if  the  sun 
happened  to  be  shining  on  one  side  of  it.  The  slight 
increase  in  temperature  caused  that  side  to  expand 
more  than  the  other,  bending  the  whole  span  as  much 
as  one  foot  out  of  the  straight.  Every  passing  cloud 
made  a  difference,  by  more  or  less  shielding  the  sun's 
rays  and  so  varying  the  temperature. 

If  the  variation  of  a  few  degrees  is  able  to  bend 
a  huge  structure  like  the  Forth  Bridge,  it  is  evident 

25 


Sources  of  Power 

what  an  enormous  power  is  to  be  obtained  from  the 
fierce  energy  of  a  furnace. 

Of  all  the  substances  which  may  be  expanded  thus 
by  the  application  of  heat,  one  of  the  most  convenient 
for  our  purpose  is  water.  Not  only  does  it  expand 
gradually  as  solids  do,  but  on  reaching  (if  unenclosed) 
a  temperature  of  212  degrees,  it  suddenly  changes 
into  steam,  increasing  its  volume  as  it  does  so  r6oo 
times. 

When  it  is  enclosed  in  a  boiler  it  cannot  of  course 
expand  ;  but  its  effort  to  do  so  produces  a  great  pressure 
— so  great  indeed  that,  if  it  were  allowed  to  continue,  it 
would  burst  the  strongest  boiler  that  could  be  con- 
structed. 

Here,  then,  we  have  a  ready  means  of  turning  the 
energy  of  coal  into  a  powerful  moving  force,  and  it 
only  remains  to  harness  this  energy  of  steam  and  turn 
it  to  the  work  that  we  require  to  be  done. 

It  is  curious  that  whereas,  now,  the  work  generally 
required  of  an  engine  is  to  turn  something  round,  the 
steam-engine  had  been  in  existence  for  pumping  water 
by  an  up-and-down  movement  for  seventy  years  before 
any  one  thought  of  making  it  turn  a  crank  and  so  produce 
a  rotating  motion.  In  fact  there  is  a  case  on  record 
in  which  a  cotton-mill  in  Lancashire  was  driven  by 
a  steam-engine  pumping  water  on  to  a  water-wheel  so 
as  to  produce  a  rotary  motion. 

The  steam-engine  consists  of  one  or  more  cylinders, 
each  of  which  has  a  piston  sliding  inside  it.  The  steam 
enters  first  at  one  end  and  then  at  the  other,  in  that 
way  pushing  the  piston  backwards  and  forwards.  This 
motion  is  conveyed  to  a  rod,  called  the  piston-rod, 
one  end  of  which  is  attached  to  the  piston,  and  which 
slides  in  and  out  through  a  hole  in  the  end  of  the 
cylinder. 

The  other  end  of  the  piston-rod  is  connected  to 

26 


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w  HKJ; 

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be  §  d  JJ"5 

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Sources  of  Power 

a  part  called  the  cross-head,  a  block  of  metal  of  a 
suitable  shape  which  slides  between  guides,  and  whose 
function  is  to  keep  the  motion  of  the  piston  and  piston- 
rod  in  a  straight  line. 

In  pumping-engines,  which  do  not  require  to  have  a 
rotary  motion,  the  piston-rod  is  sometimes  continued 
straight  to  the  pump-barrel,  but  in  most  engines  the 
movement  of  the  cross-head  is  communicated  by  means 
of  a  rod,  called  the  connecting-rod,  to  a  crank  which 
turns  the  shaft  or  spindle  just  as  the  crank  of  a  bicycle 
turns  the  chain-wheel. 

On  the  shaft  there  is  generally  a  heavy  wheel,  called 
the  fly-wheel,  the  purpose  of  which  is  to  ensure  the 
steady  running  of  the  engine.  We  are  all  familiar  with 


FIG.  i. — The  essential  parts  of  a  Steam-engine. 

the  fact  that  anything  that  is  spinning  round  tries  hard 
to  maintain  a  regular  speed  and  strenuously  resists  any 
attempt  to  increase  or  diminish  it.  In  this  way  the 
fly-wheel  of  an  engine  tends  to  prevent  any  sudden 
variation  in  the  speed  owing  to  variations  in  the  power 
of  the  steam  or  in  the  load  on  the  engine. 

The  speed  is  further  regulated  by  a  governor,  which 
generally  takes  the  form  of  two  weighted  levers  sus- 
pended from  a  revolving  spindle,  which  is  turned  by 
the  motion  of  the  engine.  If  the  speed  be  increased 
these  tend  to  fly  outwards  owing  to  the  centrifugal 
force,  and,  in  doing  so,  slightly  close  a  valve  which 
controls  the  supply  of  steam  to  the  engine.  In  this 
way  the  speed  is  brought  back  to  the  proper  number 
of  revolutions  per  minute.  If,  on  the  other  hand,  the 
speed  should  diminish,  they  close  together  and  open 

27 


Sources  of  Power 

the  valve,  giving  the  engine  more  steam  and  so  increas- 
ing the  number  of  revolutions. 

The  valves  which  regulate  the  admission  of  the 
steam  first  to  one  end  of  the  cylinder  and  then  to  the 
other,  and  at  the  same  time  permit  the  exit  of  the 
used-up  steam,  are  worked  by  the  engine  itself.  The 
most  usual  form  is  the  "  slide-valve,"  a  kind  of  box 
which  slides  to  and  fro  inside  a  steam-tight  chest, 
called  the  "steam-chest,"  on  the 
side  of  the  cylinder.  As  it  moves 
it  covers  and  uncovers  the  mouths 
of  certain  passages,  or  "  ports "  as 
they  are  called,  in  that  way  per- 
mitting fresh  steam  to  pass  from 
the  steam-chest  through  the  ports 
into  the  cylinder,  and  allowing  the 
escape  of  the  steam  which  has 
already  done  its  work. 

The  valve  is  moved  by  a  small 

FIG.  2. —The   full-line    rod  called  the  valve-spindle,  which 
circle  shows  an  eccen-  es   Qut  through   a  hole   in   the 

trie    at    one    part    of  ,      £    ,  &.  . 

its   revolution.     The    end  of  the  steam-chest,  and  is  con- 
dotted    circle    shows    nected  by  the  eccentric  rod  to  the 
its  position  half  a  re-    eccentric  on  the  shaft. 
IhtdedVir-  .heshaft        The  eccentric  is  a  round  disc  of 
on  which  it  turns.          metal,  like  a  pulley,  which  is  fixed 
on  the  shaft  and  revolves  with  it, 
about    a    point    which    is    not    its    centre,    so    that    it 
"  wobbles."     A    strap   encircles   the   circumference   of 
the  disc,  and,  as  the  latter  turns  round  (sliding  freely 
inside    the    strap),  it  pushes   the   strap   to   and    fro    a 
distance  equal  to  twice  its  eccentricity.      The  eccentric 
rod  is  attached  to  the  strap,  and  so  the  revolution  of 
the  eccentric  works  the  valves. 

Steam  is  not,  like  water  for  instance,  incompressible. 
On   the  contrary  it  is  very  elastic,  and  consequently, 

28 


Sources  of  Power 

when  under  pressure,  it  contains  an  amount  of  force 
stored  up  within  itself  which  it  would  be  foolish  to 
waste.  This  can  best  be  understood  by  picturing  what 
would  happen  were  one  to  lift  a  weight  at  the  end  of  an 
elastic  cord.  In  that  case  the  hand  would  have  to  move 
some  distance,  before  the  weight  would  be  lifted,  during 
which  time  the  elastic  would  be  stretching.  The  force 
used  in  stretching  the  elastic  would  become  stored  up 
in  it,  and  under  certain  circumstances  a  part  of  it,  at 
any  rate,  could  be  recovered.  For  suppose  that  the 
weight  having  been  lifted  some  distance,  one-half  of  it 
could  be  detached  ;  the  elastic  alone,  without  any 
further  help  from  the  hand,  would  raise  the  remaining 
half  of  the  wreight ;  and  if  that  could  be  again  halved,  it 
would  raise  the  remainder  a  further  distance,  and  so  on 
until  the  cord  had  resumed  its  normal  length. 

In  just  the  same  way,  if  the  supply  of  steam  to  an 
engine  cylinder  be  cut  off  when,  say,  one-half  only  of 
the  stroke  has  been  made,  that  which  has  already  entered 
will  expand  and  push  the  piston  the  rest  of  the  stroke. 
As  it  expands  it  will  lose  in  pressure  until,  when  the 
piston  reaches  the  further  end  of  the  cylinder,  the  steam 
(since  it  will  have  doubled  its  volume)  will  have  only 
half  the  pressure  that  it  had  to  start  with. 

By  this  arrangement  we  do  not  therefore  get  quite 
so  much  power  out  of  our  engine  as  we  should  do  by 
letting  in  steam  at  full  pressure  all  along,  but  the  loss 
of  power  will  be  less  than  a  quarter,  whereas  the  saving 
in  steam  will  be  one-half.  The  importance  of  this  to 
the  man  who  has  to  pay  for  the  coal,  is  at  once  evident. 
But  if  the  steam  is  cut  off  at  half-stroke,  or  even 
earlier,  it  is  evident  that  there  is  still  a  lot  of  force  left 
in  it  which  does  not  get  used.  The  puffing  of  a  steam- 
engine,  which  is  such  a  familiar  sound  to  us  all,  is  simply 
a  sign  of  this  useful  energy  being  wasted. 

It  is  impossible,  however,  for  reasons  which  we  need 

29 


Sources  of  Power 

not  go  into  in  detail,  to  use  up  all  this  expansive  force 
of  the  steam  in  one  cylinder,  but  the  difficulty  is  largely 
overcome  by  taking  the  steam  through  two,  three,  or 
even  four  cylinders  in  succession.  Each  of  these  is 
larger  in  diameter  than  the  preceding  one,  so  that  the 
steam  is  able  to  expand.  Of  course  it  loses  pressure  as 
it  does  so  ;  but,  having  at  each  stage  a  larger  piston  to 
push  against,  it  is  able  to  do  useful  work. 

Such  engines  are  called  compound,  triple-expansion, 
or  quadruple-expansion  respectively,  according  as  the 

steam    passes   through 

two,     three,     or     four 
cylinders. 

There  are  many  dif- 
ferent varieties  of  steam- 
engines.  For  instance, 
there  are  the  imposing- 
looking  machines  to  be 
seen  at  the  water-works 
for  pumping  water  for 
the  supply  of  our  towns. 
These  are  generally  of 
enormous  size  since,  having  to  move  vast  quantities  of  a 
heavy  and  inelastic  substance  like  water,  they  have  to 
work  slowly,  and  an  engine  which  works  slowly  needs 
to  be  of  large  size  if  it  is  to  do  much  work. 

At  the  other  extreme  are  the  small  high-speed  engines 
used  for  generating  electricity.  They  are  generally 
coupled  direct  to  the  dynamo — that  is  to  say,  the  shafts 
of  the  two  machines  are  connected  end  to  end,  and,  as 
a  dynamo  works  well  at  a  high  speed,  these  engines  are 
comparatively  small  but  designed  for  speed.  Whereas 
a  pumping-engine  usually  works  at  about  20  to  30 
revolutions  per  minute,  the  electric-light  engine  goes  at 
200  to  300. 

These  high  speeds  necessitate  very  high-class  work- 
So 


FIG.  3.— The  advantage  of  "cutting-off" 
the  steam.  The  whole  figure  repre- 
sents the  amount  of  push  given  to  the 
piston.  The  shaded  part  shows  the 
amount  given  by  the  new  steam.  The 
unshaded  part  indicates  the  amount  of 
force  which  is  got  "for  nothing." 


Sources  of  Power 

manship,  and  special  attention  has  to  be  given  to  lubri- 
cation. 

The  marine  steam-engine  is  in  principle  just  the 
same  as  the  others,  only  it  is  made  as  compact  as 
possible  so  as  to  take  up  the  minimum  of  room  in 
the  ship.  Enormous  power  is  sometimes  concen- 
trated in  a  small  space. 

As  we  shall  see,  in  a  subsequent  chapter,  the  tendency 
of  the  present  day  is  to  supersede  the  steam-engine 
in  favour  of  the  gas-engine ;  but  there  is  one  particular 
in  which  the  steam-engine  appears  to  be  likely  to 
make  inroads  into  a  region  which  has  been  almost 
entirely  occupied  until  recently  by  the  petrol-motor, 
which  is  of  course  a  form  of  gas-engine. 

There  are  steam-engines  now  on  the  market  which 
work  at  a  very  high  pressure  (1000  Ibs.  per  square 
inch)  and  at  a  very  high  speed,  so  that  they  are  very 
small  in  themselves  and  suitable  for  motor-vehicles. 
They  have  no  boiler  in  the  ordinary  sense  of  the 
word,  but  the  water  is  injected  in  the  form  of  a 
spray  on  to  a  hot  surface,  and  "  flashes"  instantly 
into  steam,  hence  the  vessels  in  which  this  takes  place 
are  usually  called  "  flash-boilers "  although  vapouriser 
would  seem  to  be  the  better  term.  In  the  opinion 
of  many  competent  judges,  these  high-pressure  steam- 
engines  with  "  flash "  boilers  will  ultimately  be  the 
type  of  engine  most  used  on  motor-vehicles.  They 
certainly  have  the  enormous  advantage  that  they  will 
start  readily,  will  reverse  easily,  and  the  speed  can 
be  regulated  from  full  speed  down  to  a  crawl,  without 
any  need  for  complicated  gearing.  The  speed  is 
regulated  by  simply  varying  the  amount  of  water  in- 
jected into  the  boiler  at  each  stroke. 

Another  essentially  modern  form  of  steam-engine 
is  the  steam-turbine.  How  modern  it  is  will  be 
realised  from  the  fact  that  it  was  only  in  1884  that 


Sources  of  Power 

Mr.  Parsons  made  the  first  one,  and  it  was  not  until 
1891  that  the  turbine  became  a  serious  competitor 
with  the  reciprocating  engine. 

It  is  true   that   in    1629   an    Italian   named  Branca 
invented  a  little  wheel  blown  round  by  steam  escaping 


FIG.  4. — This  shows  the  principle  of  the  Parsons  Turbine. 
The  curves  represent  end  views  of  a  number  of  blades. 
The  steam  coming  from  the  left  is  split  up  into  jets,  and 
deflected  by  the  fixed  blades  as  shown  by  the  cwved 
arrows.  The  jets  then  strike  the  inside  surface  of  the 
moving  blades,  and  drive  them  in  the  direction  shown  by 
the  thick  arrow.  Finally  the  steam  rebounds  off  the 
moving  blades,  in  the  direction  shown  by  the  dotted 
arrows,  to  the  next  row  of  fixed  blades. 

from  a  pipe  ;  but  it  was  only  a  toy,  and  lacked  the 
features  that  make  the  modern  turbine  a  success,  so 
that  we  may  fairly  attribute  to  the  Hon.  C.  A.  Parsons 
the  credit  of  being  the  inventor  of  the  steam-turbine. 

The  Parsons  turbine  consists  of  a  steel  drum,  called 
the  rotor,  which  revolves  inside  a  cylindrical  cast-iron 
casing.  Round  the  rotor  there  are  rows  of  small 
blades,  in  shape  very  like  that  part  of  a  pen-nib 


Sources  of  Power 

which  fits  into  the  holder.  Fixed  to  the  inside  of 
the  casing  there  are  also  rows  of  blades  similar  to 
those  on  the  rotor,  except  that  they  are  set  the 
opposite  way,  and  the  rows  are  so  placed  that  when 
the  rotor  is  put  in  the  case  and  the  latter  closed 
they  come  alternately.  First  there  is  a  row  of  blades 
fixed  to  the  casing,  then  a  row  fixed  to  the  rotor,  then 
another  row  fixed  to  the  casing,  and  so  on. 

The  steam  enters  at  one  end  of  the  casing,  and, 
seeking  an  outlet,  passes  on  towards  the  other  end. 
It  first  encounters  a  row  of  casing  blades,  which  split 
it  up  into  jets  and  direct  these  jets  on  to  the  first 
row  of  rotor-blades.  Off  these  the  steam  rebounds 
on  to  the  second  row  of  casing  blades,  and  from  them 
on  to  the  second  row  of  rotor-blades,  and  so  on.  Thus, 
as  it  passes  along  the  whole  length  of  the  turbine 
the  steam  is  continually  being  directed  on  to  the 
blades  upon  the  rotor,  and  the  combined  effect  of 
the  impact  of  the  steam  upon  a  large  number  of  these 
small  blades  (for  there  are  thousands  of  them  in  a  large 
turbine)  is  to  push  the  rotor  round  with  great  force. 

The  rotor  and  casing  are  enlarged  by  steps  towards 
the  end  at  which  the  steam  escapes,  so  that  it  has 
room  to  expand,  and  thus  the  elastic  force  within  it 
is  utilised  in  the  same  way  as  it  is  in  a  compound 
or  triple-expansion  engine.  Indeed,  it  is  one  of  the 
great  features  of  a  turbine  that  it  can  extract  and  use 
the  whole  of  the  expansive  force  of  the  steam,  so  that 
when  it  comes  out  it  has  no  more  force  left  in  it 
than  has  that  which  we  see  rising  from  the  spout  of 
a  kettle.  For  this  reason  a  turbine  can  be  made  to 
work  efficiently  with  the  steam  which  has  already  been 
used  in  a  reciprocating  engine.  Such  turbines  are 
called  "  exhaust-steam  turbines,"  and  are  often  used 
in  large  works  for  generating  electricity  by  means  of 
waste  steam  from  the  other  engines. 

33  c 


Sources  of  Power 

It  seems  strange  at  first  sight  that  a  machine  like 
this,  in  which  the  steam  simply  blows  against  something, 
should  be  so  effective.  Of  course  the  blades  are  set 
very  close  together  ;  but  it  appears  as  if  a  lot  of  steam 
must  escape  past  them  without  doing  any  good,  and 
that  an  ordinary  steam-engine,  with  its  steam-tight 
piston,  must  be  better.  It  is  not  so,  however,  as  the 
turbine  gets  more  work  out  of  the  steam  than  the 
reciprocating  engine  does. 

Yet  it  has  one  great  defect  for  many  purposes. 
From  its  nature  it  has  to  work  at  a  high  speed,  generally 
well  over  a  thousand  revolutions  per  minute.  It  can 
be  made  to  work  more  slowly,  but  then  it  loses  some 
of  its  efficiency. 

This  high  speed  does  not  matter  much  when  it 
is  used  for  driving  electrical  machinery,  as  a  dynamo 
itself  works  well  at  a  high  speed,  but  for  propelling 
ships  it  is  a  very  serious  defect. 

A  ship's  propeller,  if  it  be  turned  too  fast,  simply 
churns  up  the  water  and  so  loses  its  pushing  effect. 
It  is  quite  easy  to  see  that  the  ideal  would  be  for  the 
propeller,  which  is  of  course  simply  a  screw,  to  push 
against  perfectly  still  water.  This  is  of  course  quite 
impossible  to  attain — there  must  always  be  some  dis- 
turbance of  the  water;  but,  when  the  speed  of  the  screw 
reaches  a  certain  point,  the  disturbance  becomes  so 
great  that  power  is  actually  lost  instead  of  gained  by 
any  further  increase  in  the  speed.  The  most  effective 
speed  depends  upon  several  things,  such  as  the  shape 
of  the  boat,  the  size  and  shape  of  the  propeller  itself ; 
but  for  most  ships  it  is  well  under  a  hundred  revolutions 
per  minute,  which  is  much  less  than  the  most  effective 
speed  of  a  turbine.1 

1  In  very  fast  steamers  it  is  possible  to  arrive  at  a  compromise  between  the 
best  speed  for  the  turbine  and  the  best  speed  for  the  screw  without  seriously 
sacrificing  efficiency,  but  this  is  out  of  the  question  for  boats  of  moderate 
speed. 

34 


Sources  of  Power 

It  is  suggested  that  this  trouble  may  be  got  over  by 
making  the  turbine  drive  a  dynamo,  the  current  from 
which  could  be  used  to  work  an  electric  motor.  The 
latter  can  be  designed  for  any  desired  speed.  This 
would  also  get  over  the  reversing  difficulty,  for  a  turbine 
will  not  reverse,  whereas  a  motor  will  do  so  easily. 
An  arrangement  of  tooth-wheels  is  also  being  tried, 
but  there  are  practical  difficulties  in  the  way  of  making 
tooth-wheels  which  will  stand  the  wear  and  tear  of 
conveying  such  large  power. 

Arising  out  of  this  remark,  the  question  will  probably 
occur  instantly  to  the  minds  of  many  readers,  How 
does  a  turbine  steamer  go  astern  if  the  turbine  will  not 
reverse  ? 

The  answer  is  that  it  has  separate  "  astern  "  turbines. 
A  very  usual  arrangement  is  this.  Many  steamers 
have  three  propellers,  each  of  which  is  fixed  to  the 
end  of  a  propeller-shaft  which  passes  through  the  ship 
to  the  engine-room.  The  centre  one  is  worked  by 
what  is  called  the  "  high-pressure "  turbine.  This  is 
simply  an  ordinary  turbine,  but  reduced  in  length  so 
that  when  the  steam  has  passed  through  there  is  still  a 
good  deal  of  force  left  in  it.  This  partially  exhausted 
steam  is  then  divided  and  goes  half  to  each  of  two  "  low- 
pressure  "  turbines,  as  they  are  called.  These  again 
are  just  ordinary  turbines,  only  shorter  than  usual, 
and  each  of  them  turns  one  of  the  two  outer  pro- 
pellers. 

Then  on  each  of  these  two  outer  propeller-shafts 
there  is  also  a  second  turbine,  in  which  the  blades  are 
set  the  opposite  way,  so  that  the  steam  will  blow  it 
round  in  the  reverse  direction.  These  are  the  "  astern  " 
turbines. 

As  a  matter  of  fact,  the  two  low-pressure  turbines 
and  the  reverse  turbines  are  generally  combined  inside 
one  case.  The  ahead  blades  are  at  one  end  of  the 

35 


Sources  of  Power 

rotor  and  the  astern  blades  at  the  other,  the  outlet 
for  the  steam  being  in  the  middle.  Thus,  if  steam  be 
admitted  at  one  end,  the  shaft  will  be  turned  one  way  ; 
while,  if  it  be  admitted  the  other,  the  direction  will  be 
reversed.  I  have  explained  this  point  at  length  because 
if  any  of  my  readers  should  ever  see  the  engine-room 
on  a  turbine  steamer  and  see  apparently  only  one 
turbine  for  each  propeller,  they  would  be  puzzled  as 
to  what  had  become  of  the  astern  turbines. 

The  centre  propeller,  I  ought  to  explain,  does  not 
usually  reverse,  as  two  are  sufficient  for  going  astern. 

For  the  propulsion  of  ships,  the  Parsons  turbine  is 
almost  invariably  used,  but  for  driving  electrical  and 
other  machinery  there  are  a  number  of  others.  Of  these 
the  best  known  are  the  Curtis,  the  Westinghouse,  the 
De  Laval,  and  the  Rateau.  They  are  all,  in  the  main 
idea,  similar  to  the  Parsons,  the  variations  being  in  the 
details,  which  I  fear  would  simply  weary  my  readers 
were  I  to  attempt  to  describe  them. 

When  the  steam-engine  was  first  invented,  the  boiler 
was  simply  a  large  iron  kettle.  The  steam  was  allowed 
to  escape  when  the  pressure  reached  i  Ib.  per  square 
inch.  In  fact,  the  force  which  drove  the  early  engines 
was  the  pressure  of  the  atmosphere,  and  not  the 
direct  power  of  the  steam  at  all.  The  purpose  of  the 
latter  was  merely  to  push  the  air  out  of  the  cylinder, 
and  then,  being  itself  condensed,  leave  a  vacuum.  It 
was  ultimately  found,  however,  that  still  greater  force 
could  be  got  by  having  a  strong  boiler,  generating  the 
steam  at  considerable  pressure,  and  using  the  direct 
power  of  the  steam. 

So,  as  advances  in  the  manufacture  of  steel  and  iron 
plates  made  it  possible,  the  strength  of  boilers  increased 
and  the  pressures  used  grew  higher  and  higher,  until 
it  is  no  unusual  thing  nowadays  for  a  boiler  to  be  made 
to  withstand  a  regular  working  pressure  of  200  Ibs. 

36 


Sources  of  Power 

per  square  inch,  being  actually  tested  with  hydraulic 
pressure  to  one  and  a  half  times  that  amount. 

The  most  common  form  of  boiler  is  what  is  called 
the  Lancashire.  It  consists  of  a  large  cylinder  or  shell, 
sometimes  as  much  as  9  feet  6  inches  in  diameter  and 
30  feet  long,  built  up  of  steel  plates  riveted  together, 
with  two  large  flues,  also  made  of  steel  plates,  running 
through  it  from  end  to  end. 

It  is  set  in  brickwork  in  which  other  flues  are  formed, 
one  underneath  the  boiler  and  one  on  each  side.  The 
fires  are  made  in  the  front  ends  of  the  two  cylindrical 
flues,  and  the  heat  passes  through  them  to  the  back, 
then  dives  downwards  and  returns  through  the  under- 
neath flue  to  the  front.  On  reaching  the  front,  it 
divides  and  returns  to  the  back  along  the  two  side 
flues.  Thus  there  is  a  great  amount  of  surface  ex- 
posed to  the  heat  of  the  fires,  and  through  which  the 
heat  can  pass  into  the  water.  At  the  back  the  fumes 
enter  the  chimney  and  pass  up  into  the  atmosphere. 

The  purpose  of  a  tall  factory  chimney  is  not,  as  is 
often  supposed,  simply  to  carry  off  the  smoke  to  regions 
where  it  will  do  the  least  harm.  Its  main  duty  is  to 
create  a  strong  draught.  Sometimes,  therefore,  a  tall 
chimney  is  dispensed  with,  and  a  fan  or  a  jet  of  steam 
is  made  to  force  air  through  the  furnace.  An  existing 
engine  and  boiler  can  often  be  made  to  generate  a 
considerably  greater  power  by  adding  a  fan  or  steam- 
jet  to  increase  the  draught. 

Although,  as  we  have  just  seen,  the  hot  gases  after 
they  leave  the  fire  are  made  to  travel  a  long  distance 
through  the  various  flues  in  contact  with  the  surface 
of  the  boiler  and  so  give  up  a  great  deal  of  their  heat, 
they  are  still  at  a  very  high  temperature  when  they 
reach  the  chimney,  and  so  a  sad  waste  of  heat  occurs. 
In  order  to  save  some  of  this  an  apparatus  called 
an  "  economiser  "  is  often  used. 

37 


Sources  of  Power 

In  this  there  are  a  number  of  cast-iron  pipes,  around 
which  the  hot  fumes  pass  just  before  they  enter  the 
chimney,  and  the  water  for  feeding  the  boiler  is  passed 
through  these  pipes.  Some  of  the  escaping  heat  is 
thus  captured  and  carried  back  into  the  boiler. 

There  is  also  an  appliance  called  a  "  superheater," 
which  is  placed  at  the  back  of  the  boiler  too.  It  is 
formed  of  a  number  of  tubes  through  which  the  steam 
passes  on  its  way  from  the  boiler  to  the  engine.  These 
tubes,  like  the  economiser,  are  heated  by  the  hot  gases 
going  to  the  chimney,  and  so  a  considerable  amount 
of  heat  is  added  to  the  steam. 

The  advantage  of  this  "  superheating,"  as  it  is  termed, 
is  not  at  once  apparent.  Ordinary  steam,  as  soon  as  it 
comes  into  contact  with  a  surface  cooler  than  itself, 
such  as  the  pipes  or  the  cylinder  of  the  engine,  begins 
to  condense,  and  in  consequence  rapidly  loses  force. 
If,  however,  it  has  been  superheated,  it  has  a  certain 
amount  of  heat  which  it  can  part  with  before  conden- 
sation begins.  Therefore  the  use  of  some  of  the  waste 
heat  from  the  fires  in  this  way  effects  a  considerable 
saving  in  the  amount  of  steam  used. 

Still,  when  all  is  done,  with  the  most  up-to-date 
boiler,  and  with  superheaters  and  economisers,  the 
amount  of  heat  which  is  put  to  a  useful  purpose  is 
only  some  25  per  cent,  of  that  which  the  coal  gives 
out,  while  75  per  cent,  goes  up  the  chimney. 

There  is  another  kind  of  boiler  called  the  Cornish. 
This  is  similar  to  the  Lancashire,  except  that  it  has  only 
one  flue  through  it  instead  of  two,  and  is  generally 
rather  smaller. 

On  board  ship  the  boilers  are  somewhat  different. 
The  shell  is  much  shorter,  and  there  is  of  course  no 
brickwork.  Instead,  the  flues  pass  at  the  back  into 
a  steel  box  called  the  combustion  chamber,  and  from 
thence  the  hot  fumes  return  through  a  number  of 

38 


Sources  of  Power 

small  tubes  which  run  through  the  boiler  from  back 
to  front  above  the  flue.  These  discharge  into  a  steel 
chimney,  which  is  fixed  to  the  front  of  the  boiler  above 
the  furnace-doors. 

In  locomotives  the  boiler  is  entirely  tubular — that  is 
to  say,  there  are  no  large  flues  at  all.  The  fire  is  made 
in  a  chamber  at  the  back  called  the  fire-box.  From 
this  there  are  some  hundreds  of  steel  tubes,  about 
3  inches  in  diameter,  which  pass  right  through  the  boiler 
into  another  chamber,  called  the  smoke-box,  at  the 
extreme  front  of  the  boiler.  The  heat  from  the  fire 
therefore  passes  through  these  tubes,  which  are  entirely 
surrounded  with  water. 

The  most  modern  type  of  boiler  is  the  t(  water-tube  " 
boiler.  In  this  the  water  is  in  tubes,  and  the  heat  from 
the  fire  passes  around  them.  These  have  many  advan- 
tages. For  one  thing  the  tubes,  since  they  are  small, 
can  be  very  thin  compared  with  the  plates  of  a 
cylindrical  boiler,  and  so  the  heat  can  the  more  easily 
penetrate  through  them  to  the  water.  Then  if  anything 
should  burst,  it  would  probably  only  be  a  small  tube 
and  not  the  shell  of  the  boiler  itself,  and  so  the  danger 
is  much  reduced.  It  must  not  be  understood  from 
this  that  cylindrical  boilers  are  in  the  habit  of  blowing 
up,  for  they  are  not  ;  but  where  such  enormous  forces 
are  kept  in  thrall  there  is  bound  to  be  the  possibility  of 
an  accident,  and,  if  it  should  happen,  less  damage  is 
likely  to  result  if  the  boiler  is  of  the  water-tube  variety. 

To  describe  all  the  different  kinds  of  water-tube 
boiler  would  fill  a  whole  book,  so  I  will  only  explain 
them  in  general  terms.  There  are  always  one  or  more 
drums,  like  small  cylindrical  boilers,  at  the  top.  Then 
there  are  a  number  of  tubes,  more  or  less  vertical  in 
direction,  connected  to  the  underside  of  these.  The 
whole  thing  is  enclosed  in  a  chamber  formed  of 
brickwork  or  steel  plates,  and  the  fire  is  at  the  bottom 

39 


Sources  of  Power 

of  this  chamber.  The  heat  thus  rises  and  travels 
among  the  tubes,  heating  them  as  it  does  so.  It  is 
always  arranged  so  that  some  of  the  tubes  are  heated 
more  than  others,  with  the  result  that  a  circulation  of 
the  water  is  set  up — up  the  hot  ones  and  down  those 
that  are  less  hot.  This  adds  greatly  to  the  efficiency  of 
the  boiler. 

Water-tube  boilers  are  very  much  used  on  war-ships, 
and  also  in  electric  generating-stations,  since  they  are 
able  to  get  up  steam  very  quickly,  an  important  fact  in 
an  emergency. 

Probably  most  readers  will  think  that  they  could 
stoke  a  boiler-fire  without  any  difficulty.  It  seems  to 
be  simply  a  matter  of  taking  a  few  shovelfuls  of  coal 
and  throwing  it  into  the  furnace.  So  long  as  the  coal 
does  not  miss  the  door  altogether  and  scatter  on  the 
floor  of  the  boiler-house,  there  does  not  seem  to  be  any 
skill  required. 

This,  however,  is  quite  a  mistake.  The  coal  must  be 
put  in  in  a  thin  layer  so  that  every  particle  may  be 
completely  consumed,  and  the  new  coal  must  be  placed 
near  the  front  of  the  furnace  so  that  the  smoky  gases 
which  are  given  off  in  the  early  stages  of  combustion 
shall  be  burnt  by  having  to  pass  over  the  glowing  fire 
beyond.  Thus  unskilful  stoking  causes  smoky  chimneys, 
perhaps  followed  by  trouble  with  the  local  authorities, 
to  say  nothing  of  the  wasteful  use  of  fuel.  If  you 
watch  an  experienced  stoker  at  work  you  will  notice 
that  he  does  not  throw  the  coal  in  promiscuously,  but 
studies  his  fire  and  then  throws  the  coal  in,  giving  his 
shovel  a  dexterous  little  twist  as  he  does  so,  in  order  to 
spread  it  on  that  part  of  the  fire  which  needs  it. 

Still,  with  the  utmost  care  and  experience  this  opera- 
tion cannot  be  done  quite  satisfactorily,  and  it  needs 
the  opening  of  the  furnace-door,  letting  in  a  flood  of 
cold  air  which  lowers  the  heat  of  the  fire. 

4° 


Sources  of  Power 

Mechanical  stokers  are  therefore  often  used  now.  In 
these  the  coal  falls  down  from  the  bunker  above,  through 
a  pipe,  into  a  little  hopper.  From  this  it  is  fed  continu- 
ously in  very  small  quantities  into  the  furnace  through 
a  small  opening,  and  as  it  is  fed  in,  the  whole  of  the 
fire  is  automatically  moved  backwards  so  that  there  is 
always  a  thin  layer  of  burning  coal,  the  fresh  coal  being 
always  at  the  front.  These  conditions  are  almost  the 
ideal  for  getting  the  full  value  out  of  the  coal,  and  the 
loss  of  heat  through  the  inrush  of  cold  air  when  the 
furnace-door  is  opened  is  avoided.  Mechanical  stokers 
need,  of  course,  to  be  driven  by  some  power,  which  is 
often  an  electric  motor. 

In  some  parts  of  the  world  where  oil  fuel  is  plentiful, 
it  is  used  instead  of  coal,  and  the  same  thing  is  being 
done  more  and  more  on  naval  ships  owing  to  the  ease 
with  which  the  fires  can  be  fed  with  liquid  fuel  as  com- 
pared with  coal.  In  this  case  the  oil  is  generally  blown 
into  the  furnace  in  a  jet,  forming  a  fine  spray,  which 
bursts  into  a  cloud  of  flame  as  soon  as  it  enters. 

Wood,  too,  is  often  used  for  fuel  where  it  is  cheap, 
and  waste  products  are  sometimes  utilised.  In  iron- 
works, for  example,  the  gases  from  the  blast-furnaces 
which  at  one  time  were  discharged  into  the  air,  forming 
those  flames  which  used  to  make  such  a  magnificent 
spectacle  at  night  in  the  iron-producing  districts,  are 
now  often  led  away  and  burnt  under  the  boilers. 
Another  instance  that  occurs  to  me  is  in  the  sugar 
plantations  in  the  West  Indies,  where  the  sugar-cane, 
after  being  crushed,  is  used  for  fuel.  It  has  very  little 
heating  power,  but  it  costs  nothing,  and  so  special 
furnaces  have  been  devised  in  order  to  burn  it.  I 
mention  these  as  illustrations  of  what  is  one  of  the 
great  objects  of  modern  engineering — to  make  use  of 
waste  products. 

The  chief  dangers  with  regard  to  steam-boilers  are 

41 


Sources  of  Power 

the  possibility  of  explosion  through  too  great  pressure 
and  through  the  water  getting  too  low. 

The  safety  valve  is  intended  to  guard  against  the 
former.  It  is  a  valve  on  the  top  of  the  boiler,  which  is 
loaded  either  by  a  heavy  weight  or  else  by  a  lighter 
weight  at  the  end  of  a  lever,  so  that,  when  the  steam 
reaches  a  certain  pressure,  it  lifts  the  valve  and  some 
of  it  escapes.  Thus  the  pressure  cannot  rise  beyond 
that  point.  The  other  danger  is  guarded  against  by  a 
valve,  operated  by  a  float  inside  the  boiler.  When  the 
float  descends  below  a  certain  level,  it  opens  the  valve 
and  allows  the  steam  to  blow  a  whistle.  Another  safe- 
guard against  the  same  danger  is  a  plug  of  soft  metal 
in  the  top  of  the  flue.  This  will  not  melt  so  long 
as  it  is  in  contact  with  the  water,  but,  as  soon  as  the 
water  falls  below  it  and  leaves  it  dry,  it  melts  and  lets 
the  steam  into  the  flue,  thereby  putting  the  fire  out. 

By  discharging  the  steam  from  an  engine  into  a 
vacuum  instead  of  into  the  air  a  considerable  addition 
is  made  to  its  power,  for,  to  the  force  of  the  steam  push- 
ing on  one  side  of  the  piston,  we  add  the  force  of  the 
vacuum  pulling  on  the  other  side.  The  apparatus  by 
which  this  vacuum  is  formed  is  called  a  condenser. 

The  commonest  form  of  condenser  is  like  a  small 
tubular  boiler.  The  steam,  on  entering  the  shell,  comes 
into  contact  with  pipes  which  are  kept  cool  by  cold 
water  circulating  through  them.  The  condensed  steam 
(that  is  to  say  water),  and  any  air  which  may  get  in 
with  the  steam,  are  withdrawn  by  a  pump  known  as  the 
air-pump.  The  water  is  thus  recovered,  and  can  then 
be  pumped  back  into  the  boiler  and  used  over  again. 
Because  of  this  fact,  these  "  surface  condensers  "  as  they 
are  termed,  since  the  steam  is  condensed  by  contact 
with  a  cold  surface,  are  invariably  used  on  ships.  The 
cooling  water  is  pumped  through  the  tubes  by  another 
pump  called  the  circulating  pump. 

42 


Sources  of  Power 

The  huge  wooden  towers  which  are  often  to  be  seen 
at  electric  generating-stations  are  for  the  purpose  of 
cooling  this  circulating  water  after  it  has  become  heated 
in  the  condenser.  It  is  pumped  up  to  the  top  and 
allowed  to  fall  in  fine  spray  like  rain,  being  cooled  through 
contact  with  the  air  as  it  falls. 

At  some  generating-stations  rows  of  revolving  jets, 
like  lawn-sprinklers,  can  be  seen.  These  are  for  the 
same  purpose,  and  neither  of  these  cooling  devices  will 
ever  be  found  where  there  is  a  plentiful  supply  of  water. 

Another  form  of  condenser  is  the  evaporative.  In 
this  the  steam  is  led  through  pipes  which  are  placed  on 
the  roof  of  the  engine-house,  or  in  some  other  exposed 
place.  On  to  these  pipes  water  is  allowed  to  trickle, 
and  the  heat  of  the  steam  inside  the  pipes  causes  it  to 
evaporate  quickly.  Now  evaporation  is  always  accom- 
panied by  a  fall  in  temperature,  so  that  the  evaporation 
of  this  water  makes  the  pipes  very  cold  and  condenses 
the  steam  within.  This  is  very  curious,  and  on  the  face 
of  it  a  strange  anomaly,  as  the  steam  by  its  own  heat 
produces  the  cold  which  condenses  it.  It  reminds  one 
of  how  the  sun  is  made  hotter  by  the  heat  which  it 
loses. 

One  of  the  most  striking  features  of  modern  engineer- 
ing is  the  central  power-station.  Not  only  are  there 
the  great  stations  for  generating  electricity  for  public 
use,  but  there  is  a  central  power-station  in  most  large 
works.  Until  the  advent  of  electricity  into  practical 
engineering  a  large  factory  would  be  driven  by  a  large 
number  of  separate  steam-engines,  each  with  its  own 
boilers  ;  but  now  there  is  always  one  large  power-house, 
where  all  the  power  for  the  whole  works  is  generated 
and  from  which  it  is  distributed  by  electricity.  Thus 
there  is  scope  for  organisation  and  labour-saving  devices 
which  did  not  occur  years  ago. 

The  generating-station  of  the  London  Underground 

43 


Sources  of  Power 

Railways  at  Chelsea,  one  of  the  largest  in  the  world, 
shows  what  can  be  done  in  this  respect.  The  boilers 
are  placed  in  two  rows  on  two  floors.  The  coal  is 
unloaded  from  barges  by  means  of  electric  cranes  at 
one  end  of  the  station.  These  cranes  drop  it  into  the 
hopper  of  an  elevator,  which  carries  it  up  to  the  top  of 
the  building  and  delivers  it  to  a  conveyer,  which  takes 
it  along  just  under  the  apex  of  the  roof  and  drops  it 
into  the  coal-bunkers,  which  are  right  at  the  very  top 
of  the  building. 

From  the  bunkers  it  falls  down  shoots  into  the 
mechanical  stokers,  which  feed  it  into  the  furnaces.  The 
ashes  fall  out  of  the  grates  at  the  back  of  the  boilers, 
and  then  down  shoots  to  the  ground  floor,  where  a 
conveyer  receives  them  and  takes  them  out  of  the 
building.  It  seems  as  if  it  would  be  impossible  to  carry 
organisation  and  method  further  than  this,  as  the  whole 
boiler-house  is  almost  automatic. 


44 


CHAPTER   III 

SOURCES   OF   POWER   (continued) 
THE   GAS-ENGINE 

ONE  of  the  most  remarkable  features  of  engineering  in 
recent  years  has  been  the  rapid  development  of  the  gas- 
engine. 

It  is  but  a  short  time  since  it  was  regarded  as  only 
suitable  for  very  small  powers,  in  places  where  there 
was  not  room  for  a  steam-engine  with  its  necessary 
accompaniments — a  boiler  and  a  store  of  coal.  To-day, 
however,  it  is  driving  many  large  factories,  and,  indeed, 
it  shows  signs  of  being  a  very  serious  rival  of  its  elder 
brother  the  steam-engine. 

For  they  both  belong  to  the  same  family,  the  heat 
engines.  Heat  is  the  real  source  of  power  in  both 
cases. 

In  the  steam-engine,  as  we  have  just  seen,  the  heat 
of  the  fuel  is  generated  in  a  furnace  under  a  boiler, 
in  which  it  is  used  to  expand  water  into  steam.  The 
pressure  resulting  from  that  expansion  is  then  used  to 
push  a  piston,  and  in  that  way  the  energy  of  heat  is 
converted  into  energy  of  motion.  In  the  gas-engine, 
however,  the  fuel  is  burnt  actually  in  the  cylinder  of 
the  engine,  and  the  heat  produced  expands  certain 
gases,  causing  a  pressure  which  moves  the  piston.  So, 
once  again,  we  see  heat  converted  into  motion.  Gas- 
engines,  from  the  fact  that  the  fuel  is  burnt  in  the 
engine  itself,  are  known  also  as  "  internal-combustion  " 
engines. 

45 


Sources  of  Power 

It  will  be  interesting  at  this  point  to  see  just  what 
happens  when  gas  explodes.  All  kinds  of  matter, 
whether  solids,  liquids,  or  gases,  are  built  up  of  tiny 
particles  called  molecules.  Each  molecule,  in  turn,  is 
composed  of  two  or  more  smaller  particles  called  atoms. 
There  are  about  eighty  different  kinds  of  atoms,  and  the 
molecules  of  some  substances  are  formed  of  one  kind 
only.  Such  substances  are  called  elements.  Iron  (and 
all  the  other  metals),  carbon,  oxygen,  hydrogen,  and 
nitrogen,  for  example,  are  all  elements,  but  the  great 
bulk  of  the  things  which  we  see  around  us  are  com- 
pounds, their  different  properties  depending  upon  the 
different  combinations  of  atoms  of  which  their  molecules 
are  built  up.  A  familiar  example  of  a  compound  is 
water,  the  molecules  of  which  are  formed  of  two  atoms 
of  hydrogen  and  one  of  oxygen,  combined  together. 

Now  some  atoms  have  an  affinity  for  each  other  and 
will,  if  given  favourable  conditions,  enter  into  certain 
combinations,  and  in  many  such  cases  heat  is  given  off 
when  the  combination  occurs.  Thus,  when  we  apply 
heat  to  a  lump  of  coal  in  the  presence  of  oxygen,  the 
carbon  atoms  and  the  oxygen  atoms  set  about  com- 
bining together,  every  atom  of  carbon  being  joined  by 
two  atoms  of  oxygen  and  so  forming  the  gas  known  as 
carbon  dioxide,  or  carbonic-acid  gas.  In  just  the  same 
way,  if  hydrogen  is  heated  in  the  presence  of  oxygen 
they  will  combine,  forming  water  as  mentioned  just 
now.  This  action  of  two  elements  combining  together, 
and  generating  heat  as  they  do  so,  is  what  we  usually 
speak  of  as  burning,  or  combustion  ;  and  it  is  clear, 
from  what  has  just  been  said,  that  for  anything  to  burn 
it  must  be  in  the  presence  of  some  other  substance 
with  which  it  can  combine,  and  that  by  some  means, 
such  as  the  application  of  a  little  heat,  the  proper  con- 
ditions can  be  set  up  which  are  conducive  to  the  joining 
together  of  their  atoms. 


Sources  of  Power 

Carbon  cannot  burn  without  oxygen,  nor  can 
hydrogen  or  any  of  the  other  gases  which  go  to  make 
up  "  coal-gas."  Many  people  make  the  mistake,  for 
instance,  of  thinking  that  a  gas-holder  might  explode 
in  a  thunderstorm  ;  but  so  long  as  it  contains  coal-gas 
and  no  oxygen,  as  ought  always  to  be  the  case,  there  is 
no  danger  whatever.  An  electric  spark  might  be  in- 
troduced into  a  gas-holder  with  perfect  safety  so  long 
as  there  is  no  oxygen  present.  I  do  not  say  that  gas- 
holders never  have  exploded,  but,  when  such  a  thing 
does  occur,  it  must  be  due  to  some  abnormal  state  of 
affairs  altogether. 

When  a  solid  like  a  lump  of  coal  burns  it  does  so 
on  its  surface.  It  cannot  do  otherwise,  for  it  is  only 
on  the  surface  that  the  carbon  and  oxygen  can  come 
sufficiently  near  together.  It  must,  then,  burn  slowly. 
The  burning  of  a  gas,  on  the  other  hand,  is  very 
different,  for  it  and  the  oxygen  can  be  thoroughly  mixed 
together,  so  that  every  atom  of  the  inflammable  gas 
has  atoms  of  oxygen  near  it  with  which  it  can  combine. 
Thus,  a  large  volume  of  gas  can  be  entirely  burnt  in  an 
instant,  and  heat  is  then  generated  instantaneously,  to 
be  followed  by  an  almost  equally  sudden  expansion,  and 
it  is  that  sudden  expansion  which  we  call  an  explosion. 

But,  some  readers  may  say,  If  the  gas  is  burnt  up, 
what  is  there  to  expand  ?  True,  the  gas  has  been 
burnt  ;  but  it  is  not  correct  to  say  that  it  has  been  burnt 
up,  for  it  has  only  been  turned  into  another  gas,  and 
when  air  is  used  to  supply  the  oxygen,  there  is  the 
nitrogen  to  be  considered  as  well.  Now  nitrogen, 
which  forms  about  four-fifths  of  the  air,  is  an  unsociable 
gas  which  is  very  reluctant  to  enter  into  any  combina- 
tion, and  so  it  remains  a  passive  spectator  of  the 
burning  process  ;  yet  it  is  there,  and  aids  in  the  explo- 
sion by  suffering  expansion  by  the  heat.  This  can 
perhaps  be  made  clearer  by  a  concrete  instance. 

47 


Sources  of  Power 

Suppose  that  we  have  a  mixture  of  air  (that  is  to 
say,  oxygen  and  nitrogen)  and  a  gas  called  carbon- 
monoxide,  of  which  we  shall  hear  more  later  on  in 
this  chapter,  and  that  we  apply  a  light  to  them.  The 
heat  of  the  match,  taper,  electric  spark,  or  whatever 
it  may  be  that  we  use,  will  set  up  the  conditions  under 
which  the  carbon-monoxide  and  oxygen  can  combine, 
and  then  these  two  will  join  together  into  a  new  gas, 
carbon-dioxide. 

Thus  at  one  moment  we  have  a  volume  of  cold  gas 
consisting  of  oxygen,  carbon-monoxide,  and  nitrogen, 
while  a  moment  later  we  have,  instead,  carbon-dioxide 
and  nitrogen  in  a  highly  heated  state,  and  therefore 
greatly  increased  in  volume.  That  sudden  increase 
in  volume  is  the  explosion. 

We  see,  then,  that  a  gas  explosion  is  simply  an  in- 
stance of  burning,  exactly  the  same  as  the  burning  of  a 
coal-fire,  the  difference  being  accounted  for  by  the 
fact  that  while  a  solid  can  only  burn  gradually,1  a  gas 
can  burn  suddenly. 

We  see,  too,  that  since  the  two  gases,  whatever  they 
may  be,  combine  in  certain  definite  proportions — as,  for 
example,  two  atoms  of  hydrogen  with  one  atom  of 
oxygen,  or  two  of  oxygen  with  one  of  carbon,  and  so 
on — if  we  want  to  get  a  very  complete  combustion  of 
the  gases  in  our  mixture,  we  must  have  them  present 
in  exactly  the  right  proportions.  If  we  do  not,  there 
will  be  some  of  one  or  the  other  left  over,  after  the 
explosion,  uncombined,  since  there  was  not  sufficient 
of  the  other  for  it  to  combine  with. 

In  a  gas-engine,  then,  we  have  a  cylinder,  closed  at 
one  end  and  open  at  the  other,  and  in  the  closed  end 

1  This  does  not  apply  when  the  solid  is  in  the  form  of  very  small  particles. 
If  reduced  to  a  fine  powder,  so  that  it  can  be  thoroughly  mixed  with  air,  coal 
will  explode  just  like  a  gas.  Many  colliery  accidents  have  been  caused  in 
this  way. 

48 


Sources  or  Power 

we  place  a  quantity  of  explosive  mixture,  that  is  to  say, 
inflammable  gas  and  air  in  the  right  proportions.  Just 
as  the  piston  is  at  its  nearest  to  the  closed  end  we 
ignite  this  mixture,  and  the  explosion  which  follows 
drives  the  piston  violently  forward.  Thus;  we  see,  the 
action  of  the  gas-engine  is  quite  different  from  that  of 
the  steam-engine,  for,  instead  of  a  steady  pushing  effect, 
we  have  a  series  of  sudden  explosions.  Moreover,  it  is 


Cylinder 


Gas  Cock 


FIG.  5.— Section  of  "  National "  Gas-Engine.  The  "  water  inlet "  and  "  out- 
let "  are  for  passing  cold  water  through  a  space  round  the  cylinder,  to 
keep  it  cool. 

Notice  that  there  is  no  piston-rod,  but  that  the  connecting-rod  is  con- 
nected directly  to  the  piston. 

necessary  that  three  strokes  should  take  place  before  an 
explosion  can  occur,  so  that  we  only  get  one  power 
stroke  in  every  four,  the  other  three  being  preparatory 
strokes,  during  which  the  engine  is  getting  ready  for 
the  power  stroke. 

What  power  is  it,  then,  which  performs  these  three 
preparatory  strokes  ?  Nothing  but  the  momentum  of 
the  fly-wheel. 

Let  us  imagine  that  we  are  watching  a  gas-engine  at 
work,  and  that  an  explosion  is  just  taking  place. 

49  D 


Sources  of  Power 

The  piston  is  driven  forward,  imparting  momentum 
to  the  fly-wheel.  That  momentum  then  forces  it  back, 
and  in  so  doing  pushes  out  of  the  cylinder  the  burnt 
gas  left  in  as  the  result  of  the  explosion.  Next  it 
goes  forward  again,  this  time  sucking  in  a  fresh  supply 
of  gas  and  air,  which  the  next  backward  stroke  com- 
presses into  the  space  at  the  back  of  the  cylinder. 
Then  a  fresh  explosion  occurs,  and  the  whole  series  or 
cycle  of  operations  is  gone  through  over  again. 

The  reason  for  compressing  the  charge  of  gas  and 
air  is  that  a  much  stronger  explosion  results  than  if  it 
were  not  compressed.  In  fact  the  gas-engine  was 
invented  as  long  ago  as  1850,  but  it  was  not  until  the 
discovery  of  this  fact  in  1876  that  the  gas-engine 
became  of  practical  utility. 

The  cycle  of  four  strokes,  as  described  above,  is 
called  the  "  Otto  "  cycle,  after  the  French  engineer  who 
invented  it,  and  it  is  the  mode  of  working  adopted  in 
nearly  all  large  gas-engines. 

The  piston  of  a  gas-engine  is  longer  than  that  of  a 
steam-engine,  so  that  it  needs  no  piston-rod  and  cross- 
head  to  guide  it.  It  is  really  a  hollow  cylinder  with  one 
end  open,  and  the  connecting-rod  enters  it  at  that  end, 
and  is  connected  to  a  pin  inside  the  piston  itself. 

The  connecting-rod,  crank,  and  fly-wheel  are  practi- 
cally the  same  as  those  of  the  steam-engine.  The 
valves  which  let  in  the  mixture  and  let  out  the  spent 
gases  are  shaped  something  like  a  mushroom,  and  so 
are  called  "  mushroom  valves."  The  illustration  (Fig.  6) 
will  explain  what  they  are  like  and  how  they  work 
better  than  a  great  many  words.  Each  valve  is  kept 
closed  by  a  spring,  but  it  has  a  stalk  or  spindle,  and 
when  it  needs  to  be  opened  this  spindle  is  pushed  up 
by  a  revolving  disc  like  an  eccentric,  only  it  has  no 
strap,  called  a  cam.  There  is  generally  one  cam  for 
the  inlet  valve  and  one  for  the  exhaust  valve,  and  they 

50 


Sources  of  Power 

are  fixed  on  what  is  called  the  cam  shaft.  This  is  a 
small  shaft  turned  round  by  the  engine  itself  by  means 
of  gearing,  so  arranged  that  it  revolves  once  for  every 
two  revolutions  of  the  crank.  It  is  therefore  often 
called  the  "half-speed"  shaft,  and  the  need  for  the 
arrangement  is  clear  when  we  remember  that  if  it  went 
at  the  same  speed  as  the  crank  it  would  open  the 
exhaust  valve  not  only  during  the  exhaust  stroke  but 
also  during  the  compression  stroke,  and  so  let  out  the 
fresh  gas  during  the  compression  stroke,  just  when  it 
most  needs  to  be  kept  in. 

Sometimes  the  inlet  valve  has  no  cam,  but  the  suction 


Closed 


Open. 


-~*  This    stitk  is     ~* 
pulled  down  by 
<2  spring 

FIG.  6. — The  Mushroom  Valve,  as  used  in  Gas-Engines.  The 
Valve  is  opened  either  by  a  cam  pushing  the  stalk  upwards, 
or  by  the  suction  of  the  engine. 

of  the  engine  itself  is  relied  upon  to  open  it  at  the 
right  time. 

The  speed  of  a  gas-engine  is  regulated  by  a  governor 
like  that  used  on  a  steam-engine.  If  the  engine  goes 
too  fast,  the  governor  either  causes  it  to  miss  an 
explosion  or  two,  or  else  reduces  the  supply  of  gas,  and 
so  makes  the  explosions  weaker,  until  it  has  resumed  its 
proper  speed. 

The  explosion  is  caused  in  one  or  two  ways.  In 
some  cases  an  electric  spark  is  made  to  pass  between  the 
ends  of  two  wires  which  project  inside  the  cylinder, 
while  in  other  cases  there  is  fitted  to  the  end  of  the 
cylinder  a  small  tube,  which  is  kept  red  hot  either  by 


Sources  ot  Power 

the  hot  exhaust  gases  from  the  engine  or  by  a  gas  jet 
outside  the  cylinder,  and  things  are  so  adjusted  that 
just  at  the  end  of  the  compression  stroke  the  gas  finds 
its  way  into  the  hot  part  of  this  tube  and  is  exploded 
by  the  heat.  The  former  method  has  the  merit  of 
being  more  easily  regulated,  so  that  the  explosion  shall 
occur  at  exactly  the  right  moment,  while  the  second  is 
considered  more  reliable.  When  electricity  is  used  it 
is  obtained  from  a  tiny  dynamo  called  a  magneto  driven 
by  the  engine,  or  else  from  a  storage  battery. 

It  would  seem  from  what  has  been  described  above 
that  the  action  of  a  gas-engine  must  be  jerky  and 
spasmodic,  and  such  is  no  doubt  actually  the  case.  By 
having  the  flywheel  sufficiently  heavy,  however,  and 
working  the  engine  at  a  fairly  high  speed,  the  variations 
become  so  slight  that  for  practical  purposes  the  engine 
may  be  regarded  as  quite  steady  and  regular  in  its 
motion. 

One  of  the  defects  of  the  gas-engine  is  that  it  will  not 
readily  start  itself.  It  cannot  possibly  do  so,  as  the 
three  preparatory  strokes  have  to  be  performed  before 
the  power  stroke  is  possible.  In  the  case  of  small 
engines  this  can  easily  be  overcome  by  turning  the 
engine  round  a  few  times  by  hand.  Another  way  still 
is  to  have  a  hand  pump,  by  which  the  explosive 
mixture  can  be  compressed  into  the  cylinder  and  the 
compression  stroke  of  the  engine  thus  imitated. 
Another  way  still  is  to  let  the  engine,  when  it  is 
working,  pump  up  a  store  of  compressed  air  in  a 
reservoir.  Then,  when  the  engine  needs  to  be  started, 
some  of  this  compressed  air  is  allowed  to  enter  the 
cylinder  and  push  the  piston.  A  few  strokes  having 
been  made  like  this,  sufficient  impetus  will  have  been 
acquired  for  it  to  perform  its  three  preparatory  strokes, 
and  so  start  working  in  the  normal  way. 

The  reversal  of  a  gas-engine,  too,  is  not  so  easy  as 

52 


Sources  of  Power 

that  of  a  steam-engine.  It  is  an  easy  matter  to  alter 
the  action  of  the  cams  so  as  to  cause  the  engine  to 
work  in  the  opposite  direction,  but  it  generally  has  to 
be  stopped  and  restarted,  all  the  difficulties  described 
above  being  consequently  encountered.  With  a  steam- 
engine,  on  the  other  hand,  both  the  starting  and 
reversing  can  be  accomplished  by  the  simple  move- 
ment of  a  handle. 

Ordinary  coal-gas,  such  as  is  used  for  lighting,  was, 
until  a  few  years  ago,  invariably  used  to  drive  gas- 
engines,  but  now  there  is  a  cheaper  gas,  known  as 
"  producer  gas,"  which  answers  the  purpose  almost  as 
well  and  is  very  much  cheaper.  Moreover,  it  can  be 
generated  in  a  simple  little  contrivance,  called  a  "  suc- 
tion producer,"  with  very  little  trouble  and  with  perfect 
safety.  It  is  this  cheap  gas  which  has  brought  about 
such  a  remarkable  increase  in  the  use  of  gas-engines 
during  the  last  few  years. 

Producer  gas  is  made  from  coal  or  coke,  and  it 
consists  mainly  of  a  gas  called  carbon-monoxide,  and 
hydrogen.  It  is  different  from  coal  gas  in  that  the 
latter  is  distilled  from  coal  by  merely  heating  it, 
while  the  former  is  made  by  actually  burning  the 
coal. 

Coal  and  coke  are  both  impure  forms  of  carbon,  and 
when  heated  sufficiently  the  carbon  will  combine  with 
oxygen  from  the  air,  forming  carbon  dioxide,  other- 
wise carbonic-acid  gas.  This  is  what  occurs  in  an 
ordinary  coal  fire.  This  gas,  as  we  already  know, 
consists  of  molecules  each  made  up  of  one  atom  of 
carbon  and  two  atoms  of  oxygen.  It  will  not  admit 
any  more  oxygen  into  the  arrangement,  and  so  it  will 
not  burn. 

If,  however,  it  is  brought  into  contact  with  some 
more  carbon  in  a  highly  heated  state,  the  three  atoms 
just  referred  to  are  joined  by  another  atom  of  carbon, 

53 


Sources  of  Power 

so  that  there  are  then  two  of  each  kind.  Instead  of 
taking  the  additional  atom  in  and  forming  a  quadruple 
partnership,  however,  the  four  atoms  pair  off  and  form 


Lid 


Sliding  Door 


FIG.  7. — Diagram  showing  the  construction  of  a  Suction  Gas  Producer.  To 
charge  the  producer,  the  Hopper  is  filled  with  coal  and  the  lid  closed. 
Then  the  Sliding  Door  is  opened,  and  the  coal  falls  in.  So  the  coal  is 
put  in  without  letting  any  air  in. 

themselves  into  two  molecules,  each  made  up  of  one 
atom  of  carbon  and  one  of  oxygen.  Those  molecules 
constitute  carbon-monoxide. 

Now  when  carbon  and  oxygen  combine  into  carbon 

54 


Sources  of  Power 

dioxide,  heat  is  liberated  (hence  the  heat  of  a  coal  fire), 
but  when  that  is  converted  back,  as  just  described,  into 
carbon-monoxide,  heat  is  consumed.  We  have  to 
provide  a  supply  of  heat  from  some  source  in  order  to 
force  the  atoms  to  make  the  change.  If,  however, 
we  bring  some  more  oxygen  into  contact  with  the 
carbon-monoxide,  and  give  it  just  a  little  heat,  we 
shall  get  carbon-dioxide  once  more,  and  when  that 
change  occurs  the  heat  just  referred  to  is  liberated  again. 
Or  we  may  put  it  that  carbon-monoxide,  if  mixed  with 
air,  will  burn.  Those  beautiful  blue  flames  which  can 
be  seen  hovering  over  a  deep  fire,  such  as  those  often 
made  by  night-watchmen  in  an  old  bucket,  are  the 
burning  carbon-monoxide. 

Now  let  us  examine  the  plant  in  which  these  changes 
are  carried  out  quietly  and  automatically.  There  is  an 
iron  cylinder,  lined  with  firebrick  and  set  up  on  end. 
At  the  bottom  of  this  there  is  a  grate  on  which  a  fire  is 
made,  and  then  the  whole  thing  is  filled  right  up  to  the 
top  with  coal.  Under  the  grate  there  is  an  inlet  for 
air,  and  at  the  top  (which,  by  the  way,  is  entirely  covered 
in)  there  is  an  outlet  connected  to  a  pipe  which  leads 
ultimately  to  the  engine.  At  every  suction  stroke  of 
the  engine  some  air  is  drawn  in  at  the  bottom  and 
passes  up  through  the  fire.  The  coal  at  the  bottom  of 
the  producer  is  thus  kept  burning,  and  the  air  as  it 
enters  is  soon  transformed  into  carbon-dioxide.  Since 
all  the  oxygen  in  the  air  is  thus  used  up  soon  after  it 
enters  the  furnace,  the  coal  only  burns  just  at  the 
bottom.  That  which  is  higher  up  cannot  burn  for 
lack  of  oxygen,  so  it  becomes  a  very  hot,  but  not 
burning,  mass  of  carbon.  Now  the  carbon-dioxide 
formed  in  the  fire  at  the  bottom  has  to  pass  up  through 
this  mass  of  hot  carbon,  and  in  so  doing  it  is  changed 
into  carbon-monoxide.  Thus,  although  it  is  only  the 
product  of  a  coal  fire,  it  is  not  the  incombustible  gas, 

55 


Sources  of  Power 

carbon-dioxide,  which  passes  out  to  the  engine,  but  the 
burnable  monoxide. 

In  order  to  save  some  of  the  waste  heat  which 
escapes  from  the  furnace  there  is  placed  in  some 
suitable  position  a  vapouriser,  a  vessel  containing 
water  which  will  be  heated  by  the  escaping  heat.  A 
certain  amount  of  the  water  is  thus  turned  into  steam, 
which  is  carried  down  by  a  pipe  to  the  bottom  of  the 
producer  and  introduced  under  the  grate.  It  is  then 
sucked  up  through  the  fire.  Now  steam,  we  already 
know,  consists  of  oxygen  and  hydrogen  in  combination, 
and  when  it  is  passed  through  a  heated  mass  like  this, 
it  is  split  up  into  these  two  elements.  The  oxygen 
immediately  combines  with  some  of  the  carbon,  form- 
ing more  monoxide,  while  the  hydrogen  passes  on  to 
the  engine,  and  so  enriches  the  mixture. 

There  are  certain  other  products  which  arise  from 
the  coal,  but  these  two  are  the  principal  ones.  After 
leaving  the  producer  the  gas  goes  through  a  "  scrubber," 
as  it  is  called.  This,  again,  consists  of  a  vertical  iron 
cylinder,  filled  with  coke,  through  which  the  gas  has  to 
find  its  way.  As  it  passes  upwards  it  meets  water, 
Which  is  sprayed  on  to  the  top  of  the  coke  and  trickles 
down  through  it.  This  cleans  the  gas,  cools  it,  and 
also  removes  dust  which  might  get  info  and  clog  the 
cylinder  of  the  engine. 

At  present  only  coke  or  anthracite  coal  can  be  used 
in  these  producers,  as  ordinary  coal  contains  tarry  pro- 
ducts which  cannot  be  removed  in  a  small  plant,  and 
which,  if  they  were  not  removed,  would  form  soot  in 
the  cylinder  of  the  engine. 

The  economy  of  these  suction  producer  plants  is  so 
great  that,  even  in  a  very  small  plant,  power  can  be 
produced  at  the  rate  of  ten  horse-power  for  an  hour 
for  a  penny.  The  gas  is,  however,  not  quite  so 
powerful  as  coal  gas,  so  that  an  engine  working  on 

56 


Sources  of  Power 

producer  gas  has  to  be  slightly  larger  to  give  the  same 
power. 

The  waste  gas  which  comes  from  the  blast  furnaces 
at  an  ironworks  is  largely  carbon-monoxide,  and  it  is 
very  frequently  used  to  drive  gas-engines. 

Gas-engines  have  not  yet  been  used  to  any  extent 
for  marine  purposes  except  in  the  case  of  small  boats 
driven  by  small  gas-engines  using  vapourised  oil  as  the 
gas,  some  of  which  will  be  described  later,  and  some 
tugs  on  the  Rhine  which  have  gas-engines  and  suction 
producers. 

It  will  soon  come,  however — of  that  there  can  be 
no  doubt,  and  at  the  moment  of  writing  this  there  is 
being  designed  a  small  cargo  " steamer"  driven  by  a 
gas-engine  and  suction  producer. 

The  great  difficulty  is  with  the  speed  and  the  re- 
versing, as  mentioned  in  the  last  chapter  in  connection 
with  steam-turbines,  and  in  the  case  referred  to  the 
same  method  of  overcoming  it  is  being  tried.  The 
engine  (which  has  six  cylinders  by  the  way)  is  to  run 
at  an  invariable  speed  of  500  revolutions  per  minute, 
and  it  will  drive  a  dynamo  which  will  supply  current 
to  an  electric  motor,  which  will  turn  the  propeller  at  a 
speed  of  only  80  revolutions  per  minute.  The  speed 
of  the  propeller  will  be  varied  electrically,  and  it  will  be 
reversed  by  the  same  means,  so  that  the  speed  and 
direction  of  the  engine  will  remain  constant  under  all 
circumstances — just  the  conditions  under  which  a  gas- 
engine  works  best  and  most  economically. 

On  small  boats  and  for  light  jobs,  oil-engines  are 
often  used.  These  are  mostly  exactly  the  same  as 
gas-engines,  except  that  there  is  an  additional  part 
called  a  "  vapouriser,"  in  which  the  oil  is  heated  and  so 
turned  into  vapour.  Very  often  this  is  simply  an  ex- 
tension of  the  back  part  of  the  cylinder,  which  is,  at 
starting,  heated  by  a  lamp  outside.  When  once  it  is 

57 


Sources  of  Power 

hot  enough  and  the  engine  is  going,  the  lamp  is  no 
longer  needed,  however,  for  the  heat  of  the  explosions 
is  sufficient  to  keep  the  vapouriser  hot.  At  each 
"  charging  "  stroke  a  little  oil  is  sucked  in  by  the  action 
of  the  engine.  This  falls  into  the  hot  vapouriser,  and 
is  turned  immediately  into  vapour,  which  is  com- 
pressed and  exploded  exactly  as  the  gas  is  in  a  gas- 
engine. 

There  is  one  kind  of  oil-engine,  however,  which 
must  be  mentioned  specially,  as  it  does  not  work  quite 
like  an  ordinary  gas-engine  ;  indeed  it  may  be  said 
that  it  has  no  "  explosion "  stroke.  It  is  called  the 
"  Diesel "  engine,  after  its  inventor. 

During  the  charging  stroke  the  engine  draws  in  pure 
air — not  air  and  oil.  By  the  next  stroke  this  air  is 
compressed  to  about  500  Ibs.  per  square  inch  pressure, 
and  that  compression  raises  it  to  a  temperature  of 
about  1000°,  which  is  sufficiently  hot  to  ignite  the 
oil.  When,  therefore,  at  the  commencement  of  the 
"  power  "  stroke,  a  jet  of  oil  is  forced  into  the  cylinder 
by  a  pump,  it  begins  at  once  to  burn,  and  continues  to 
do  so  steadily  so  long  as  the  jet  lasts.  Instead  of  an 
explosion,  therefore,  we  have,  in  this  engine,  a  steady 
burning,  and  by  varying  the  duration  of  the  jet,  the 
speed  of  the  engine  can  be  regulated  to  a  nicety.  Such 
an  engine,  it  is  clear,  needs  no  vapouriser,  and  none  of 
the  devices  for  igniting  the  gas  which  so  often  give 
trouble  in  other  engines. 

The  petrol  motor  is  also  a  type  of  gas-engine,  but 
it  is  of  such  importance,  and  appears  in  so  many  dif- 
ferent forms,  that  it  cannot  be  dealt  with  adequately 
at  the  end  of  an  already  lengthy  chapter.  It  will, 
therefore,  be  referred  to  later  on. 

It  would  be  impossible  to  conclude  this  chapter 
without  reference  to  the  most  modern  of  all  forms  of 
gas-engine — the  internal-combustion  pump.  It  may 

58 


Sources  of  Power 

be  described  as  a  gas-engine  in  which  the  piston, 
connecting-rod,  and  fly-wheel  are  all  composed  of  water. 

To  understand  this  remarkable  machine  it  will  be 
necessary  to  turn  to  the  diagram  (Fig.  8).  There  are 
two  tanks,  a  lower  one  containing  the  water  to  be 
pumped  and  a  higher  one  into  which  the  water  is 
delivered  by  the  pump. 

Let    us   look    at   it    as    we  did    at    the    gas-engine, 


very 


Gas  Inlet- 


Tank 


FIG.  8. — Sectional  diagram  showing  how  the  "Humphry" 
Internal  Combustion  Pump  works. 

assuming  that  an  explosion  is  taking  place.  The  water 
in  the  cylinder  is  just  commencing  to  be  driven  down- 
wards, and,  since  the  mushroom  valves  at  ^/prevent  it 
from  going  to  the  suction  tank,  it  is  bound  to  go  to  the 
delivery  tank.  The  explosion,  of  course,  does  not 
force  it  very  far,  but  the  column  of  water  in  the  pipe 
still  continues  to  move  a  little  further,  because  of  its 
momentum,  after  the  force  of  the  explosion  has  spent 
itself,  and  during  that  time  it  sucks  in  fresh  water  from 
the  suction  tank,  and  also  some  air  through  a  valve  at 
the  top.  Then,  since  the  delivery  tank  is  higher  than 

59 


Sources  of  Power 

the  cylinder,  the  water  begins  to  gravitate  back,  and  in 
so  doing  it  pushes  out  the  spent  gas  through  the 
exhaust  valve,  closes  the  valve  itself,  and  finally  entraps 
some  air  in  the  space  C  which  it  compresses.  This  air, 
acting  like  a  spring,  first  gives  way  before  the  moving 
water  and  then  rebounds,  as  it  were,  and  drives  the 
water  downwards  once  more.  Again  the  momentum 
of  the  moving  water  causes  it  to  "  suck,"  and  this  time 
it  draws  gas  in  through  the  inlet  valve,  returning  a 
moment  later  to  compress  it,  after  which  another 
explosion  takes  place. 

So  the  same  cycle  is  gone  through  over  and  over 
again,  and  it  will  be  seen  that  it  is  really  exactly  the 
same  as  the  "  Otto  "  cycle  in  an  ordinary  gas-engine, 
the  oscillation,  or  surging  to  and  fro  of  the  water  in 
the  pipe,  doing  the  work  of  the  fly-wheel. 

This  is  the  most  efficient  internal-combustion  motor 
in  existence,  since  it  uses  a  greater  percentage  of  the 
force  of  the  explosion  than  any  other  form  of  engine 
can  do.  Its  working  parts,  too,  are  few  and  small,  so 
there  is  little  to  wear,  little  to  lubricate,  and  little  to  get 
out  of  order,  as  the  water  itself  forms  the  main  work- 
ing parts.  For  this  reason  it  may  be  found  economical 
to  use  it  for  supplying  water  to  a  water-turbine,  and 
so  driving  machinery;  or  it  may  revolutionise  the 
methods  of  propelling  ships,  for  it  has  long  been  known 
that  a  jet  of  water  issuing  from  the  stern  of  a  ship  is 
much  more  effective  than  a  screw-propeller,  only  until 
now  a  suitable  pump  has  not  been  forthcoming  to 
form  the  jets.  It  may  be  that  here  is  the  solution  of 
the  difficulty. 


60 


CHAPTER   IV 

SOURCES  OF  POWER  (continued} 
RUNNING     WATER 

MY  task  in  describing  the  most  modern  methods  of 
securing  and  turning  to  account  the  power  which  is  to 
be  obtained  from  running  water  will  be  rendered  much 
simpler  if  I  give  a  description  of  a  great  installation  in 
the  United  States  ;  one  of  the  finest  examples  of  a 
water-power  plant  that  the  world  possesses. 

There  may  not  be  quite  the  same  glamour  about  it 
that  there  is  surrounding  the  famous  installation  at 
Niagara  Falls,  but  in  one  sense  it  is  far  more  interesting, 
for  while  there  is  only  one  Niagara  in  half  a  world 
there  are  rivers  in  many  countries  which  might  be 
harnessed  and  set  to  work  as  is  being  done  with  the 
Susquehanna  at  McCall  Ferry,  in  Pennsylvania. 

This  spot  is  a  little  over  twenty  miles  from  the  mouth 
of  the  river,  forty  miles  from  Baltimore,  and  sixty-five 
from  Philadelphia. 

Here  a  huge  dam  has  been  thrown  across  the  river 
2500  feet  long  and  from  40  to  80  feet  high,  making 
it  one  of  the  largest  in  the  world,  and  by  its  means 
some  of  the  water  is  forced  to  pass  through  water- 
turbines,  which,  when  the  work  is  complete,  will 
be  capable  of  producing  120,000  horse-power,  to  be 
conveyed  electrically  to  the  neighbouring  towns.  It 
will  be  evident  that  the  construction  of  such  a  dam, 
right  across  a  rapid  river,  was  no  light  task.  The  first 
thing  to  be  done  was  to  build  temporary  dams,  called 

61 


Sources  of  Power 

"  cofferdams,"  to  keep  the  water  back  and  leave  a  part 
of  the  river-bed  dry.  Huge  timber  "  cribs  "  or  boxes 
were  made  and  filled  with  rock,  so  that  they  would  sink 
in  the  river  ;  these  were  placed  in  the  water,  about  ten 
feet  apart.  The  bed  of  the  river  is  of  rock,  which 
naturally  is  a  great  advantage  when  a  dam  is  to  be 
built,  since  it  forms  a  thoroughly  sound  foundation, 
and  the  cribs  were  shaped  to  fit  exactly  the  shape  of  this 
rocky  floor.  The  shape  was  ascertained  by  anchor- 
ing a  boat  over  the  spot  and  taking  careful  sound- 
ings. When  the  cribs  had  been  accurately  sunk  in 
position,  strong  horizontal  timbers  twelve  inches  square 
were  placed  in  between  them,  and  these  were  covered 
with  vertical  planks.  Finally  bundles  of  brushwood, 
weighted  with  stones  to  make  them  sink,  were  thrown 
into  the  water  and  covered  with  clay  and  sand  so  as  to 
form  a  solid  embankment.  The  structure  was  then 
quite  water-tight,  and  by  its  means  practically  the  whole 
of  the  water  of  the  river  was  diverted  into  one  half  of 
the  river-bed,  having  the  other  half  dry. 

In  the  dry  space  thus  formed  a  bridge  was  built,  to 
facilitate  the  conveyance  of  the  concrete  and  other 
materials  from  the  bank  to  the  site.  It  is  usual  on  a 
job  like  this  for  the  temporary  bridge  to  be  a  light 
trestle  structure,  supported  on  piles,  but  in  this  case  it 
was  thought  that,  owing  to  the  heavy  floods  to  which 
the  river  is  subject,  a  bridge  of  that  description  would 
probably  be  carried  away.  A  substantial  concrete  arch 
viaduct  was  therefore  made,  first  of  all  from  one  bank 
to  an  island  in  the  middle  of  the  river  and  later  from 
the  island  to  the  further  bank.  This  bridge,  although 
it  is  only  temporary — a  mere  tool  or  appliance  used  in 
the  construction  of  the  dam — is  59  feet  wide,  itself  a 
work  of  no  mean  order.  It  carries  several  lines  of 
railway  track,  of  standard  gauge,  besides  special  tracks 
for  huge  travelling  cranes. 

62 


Sources  of  Power 

It  was  built  just  on  the  down-stream  side  of  where 
the  dam  itself  was  to  be,  so  that  cranes  upon  it  could 
easily  reach  over  and  drop  huge  tubs  full  of  concrete 
right  into  the  required  place.  Except  for  a  small 
portion  of  it,  which  will  form,  ultimately,  a  part  of  the 
foundations  of  the  power-house,  it  will  all  be  blown 
up  with  dynamite  when  the  permanent  work  is  com- 
plete. 

Next  a  long  level  platform  of  concrete  was  laid,  on 
the  solid  rock,  to  form  the  foundation  of  the  dam,  and 
upon  it  the  dam  itself  was  raised. 

This  too,  was  made  entirely  of  concrete,  a  material 
which  is  coming  into  use  more  and  more  every  day,  in 
engineering  works.  It  is  formed  by  mixing  stones  and 
sand  with  Portland  cement  in  suitable  proportions. 

In  this  case,  as  such  an  enormous  quantity  of  it  was 
required,  special  methods  of  mixing  were  devised.  The 
material  arrived  on  the  spot  by  railway,  in  trucks  called 
"  dumping  cars,"  since  the  bottoms  can  be  let  down 
and  the  whole  contents  "  dumped  "  in  a  few  seconds. 
The  line  was  made  to  pass  over  huge  storage  bins, 
some  for  rock,  some  for  sand,  and  some  for  cement,  so 
that  the  material  could  be  dropped  out  of  the  cars 
straight  into  its  proper  bin.  Under  these  bins  there 
was  a  tunnel  in  which  ran  measuring  cars.  Each  of 
these  would  stop,  first  of  all,  under  the  cement  bin ;  a 
door  would  be  opened,  and  the  right  quantity  of  cement 
shot  into  it ;  then  in  like  manner  it  passed  under  the 
sand  and  stone  bins,  receiving  from  them  the  correct 
proportions  of  sand  and  rock,  after  which  it  passed,  but 
a  short  distance,  to  the  concrete-mixing  machine,  into 
which  it  discharged  the  whole  of  its  contents. 

A  concrete-mixer  is  a  simple  machine  in  which  all 
these  materials  are  well  and  thoroughly  mixed  together, 
with  the  proper  quantity  of  water.  There  were  eight 
of  them  used  on  this  job,  and  each  had  two  of  the 

63 


Sources  of  Power 

measuring  cars  in  attendance  upon  it,  one  discharging 
while  the  other  was  loading,  so  that  the  work  went  on 
continuously. 

The  storage  bins  were  capable  of  holding  14,000 
cubic  yards  of  material,  and  the  mixers  turned  out  the 
finished  concrete  at  the  rate  of  2300  cubic  yards  per 
day.  It  is  difficult  to  realise  the  magnitude  of  cubic 
measure;  a  yard  in  length  does  not  seem  much,  but 
a  cubic  yard  contains  an  astonishing  quantity  of  mate- 
rial, so  that  the  real  meaning  of  the  above  quantities 
will  be  better  understood  if  they  are  stated  in  this  way : 
a  store  of  over  20,000  tons  of  material  was  kept,  to 
draw  from,  and  this  was  turned  into  concrete  at  the 
rate  of,  roughly,  4000  tons  per  day.  There  we  get  a 
much  better  idea  of  the  vastness  of  the  undertaking. 

The  concrete,  after  passing  through  the  mixer,  was 
discharged  into  buckets  containing  one  yard  each, 
resting  upon  railway  trucks,  and  these,  in  trains  of 
about  five  trucks,  were  hauled  out  along  the  temporary 
bridge  by  steam  locomotives. 

On  arrival  at  the  spot  where  the  actual  building  of 
the  dam  was  in  progress,  each  bucket  was  picked  up 
by  a  peculiar  kind  of  crane,  called  a  "  pelican  crane," 
from  its  fancied  resemblance  to  that  curious  bird. 
These  cranes  consist  of  a  strong  framework,  from  which 
there  extend  upwards,  on  one  side,  long  inclined  arms, 
over  100  feet  long,  so  that  the  crane  can  stand  on 
the  bridge  and  reach  right  over  where  the  dam  is 
being  built.  The  bucket  is  picked  up  off  the  truck, 
at  a  point  near  the  bottom  of  the  inclined  arm,  and 
is  then  carried  outward  until  it  has  reached  the  right 
spot,  when  the  bottom  of  the  bucket  is  let  fall,  and  the 
concrete  drops  into  its  place. 

Concrete  is,  of  course,  different  from  such  materials 
as  brick  or  stone,  in  that  it  needs  to  have  a  mould  or 
form,  to  hold  it  in  the  desired  shape  until  it  has  set, 


Sources  of  Power 

and  in  concrete  work  the  construction  of  these  moulds 
often  costs  more  than  the  concrete  itself,  so  that  it  is 
always  important  to  reduce  this  cost  as  much  as  pos- 
sible. In  this  undertaking  steel  frames  were  designed 
specially,  as  shown  in  the  accompanying  drawing  (Fig.  9), 
which  supported  a  casing  of  timber  forming  a  huge 
box,  the  shape  of  the  dam,  which  was  filled  with  con- 


Rotk 

FIG.  9.  —  Diagram  showing  how  the  Concrete  Dam  was  formed. 
Steel  beams  as  at  A,  A,  A  formed  frames,  at  intervals,  from 
which  short  steel  props  supported  boarding,  which  formed 
a  complete  box.  The  concrete  was  filled  into  this  box, 
and  when  set,  the  frames  and  boarding  were  removed. 

The  dam  is  nearly  60  feet  high,  and  70  feet  wide  at  the 
bottom. 


crete.  The  dam  was  thus  built,  in  sections  40  feet 
long,  and  as  soon  as  one  section  had  set  the  framing 
could  be  separated  into  a  few  parts,  lifted  up  by  a 
crane,  and  taken  away  to  be  used  in  the  same  way  for 
another  section. 

The  drawing  just  referred  to  also  shows  us  the 
shape  of  the  dam.  The  vertical  side  is  the  upstream 
face,  against  which  the  force  of  the  water  will  press, 
while  the  curve  is  on  the  downstream  side,  so  as  to 
form  a  kind  of  prop  against  the  pressure  of  the  water. 

65  E 


Sources  of  Power 

It  is  unlike  many  dams,  which  have  a  flat  top  with  a 
roadway  upon  it,  for  the  river  is  subject  to  violent 
floods,  and  it  is  necessary  that  the  flood  waters  should 
have  plenty  of  space  in  which  to  fall  over  the  dam, 
as  otherwise  serious  damage  might  be  done.  As  a 
matter  of  fact,  in  times  of  flood  there  will  be  a  depth 
of  1 8  feet  of  water  on  the  top  of  the  dam,  so  that  re- 
garded merely  as  a  waterfall  it  will  be  an  imposing 
spectacle. 

A  good  illustration  of  the  difficulties  which  engineers 
have  to  face,  and  which  are  probably  quite  unsuspected 
by  the  general  public,  is  furnished  by  this  dam.  Who- 
ever would  expect  that  a  concrete  structure  of  these 
dimensions,  always  in  contact  with  water,  would  be 
liable  to  damage,  if  not  to  destruction,  from  the 
expansion  and  contraction  due  to  changes  in  tempera- 
ture ?  Yet  such  is  the  case,  and  if  no  provision  were 
made  and  scope  allowed  for  the  play  of  this  irresistible 
force,  the  solid  concrete  would  soon  be  rent  by  cracks 
and  fissures. 

As  mentioned  just  now,  the  dam  was  built  in  sections 
of  40  feet,  and  between  these  sections  layers  of  tar  paper 
have  been  put.  This  forms  a  soft  elastic  joint,  giving 
play  to  the  forces  of  expansion  and  contraction,  and  so 
enabling  them  to  expend  themselves  harmlessly. 

All  the  machinery  employed  was  worked  by  pneu- 
matic pressure.  Two  large  air-compressors  were  used, 
driven  by  steam,  and  the  air  from  them  was  conveyed 
by  pipes  to  the  machines.  The  concrete-mixers  and 
the  pelican  cranes,  besides  a  host  of  smaller  tools, 
were  all  operated  by  compressed  air  motors. 

And  now,  the  question  may  be  asked,  What  is  the  use 
of  this  great  dam  ?  What  purpose  does  it  serve  ?  It 
is  simply  to  produce  a  difference  in  level  in  the  water. 
The  force  with  which  water  issues  from  the  ordinary 
domestic  water  tap  is  due  to  a  difference  in  level — the 

$6 


Sources  of  Power 

difference,  namely,  between  the  level  of  the  tap  and  that 
of  the  cistern  up  near  the  roof  of  the  house.  For  this 
reason  the  water  will  come  out  of  a  tap  on  the  ground 
floor  much  faster  than  it  will  out  of  a  tap  in,  say,  a 
bathroom  one  or  two  floors  higher  up.  At  these  upper 
floors,  the  difference  in  level,  or  {t  head  "  of  water,  to 
use  the  technical  term,  will  be  much  less,  and  so  the 
pressure  will  be  less  in  proportion.  Speaking  roughly, 
every  two  feet  of  head,  or  difference  in  level,  will 
produce  one  pound  per  square  inch  of  pressure. 

The  ordinary  fall  in  a  river,  even  it  be  a  rapid  one, 
is  gradual,  so  that  in  order  to  be  able  to  take  advantage 
of  the  force  of  the  stream  a  dam  must  be  constructed  ; 
this  raises  the  level  of  the  water  on  the  upstream  side, 
and  then,  if  it  be  allowed  to  pass  through  a  pipe  or 
channel  from  the  higher  to  the  lower  level,  it  will  rush 
through  with  a  force  due  to  the  difference  in  level. 
Suitable  machines  can  then  be  placed  in  this  pipe  or 
channel,  and  the  water  as  it  rushes  through  will  work 
them. 

Of  course,  care  needs  to  be  exercised  in  choosing  a 
site  for  a  dam,  because  raising  the  level  of  the  water 
will  cause  the  river  to  rise  higher  up  its  banks  for 
several  miles  back,  and  if  the  banks  should  be  fairly 
flat  the  water  would  simply  overflow.  The  banks,  for 
some  distance  above  the  dam,  therefore,  need  to  be 
steep  enough  to  hold  the  river  even  at  its  higher  level. 

The  "  weirs  "  on  a  river  are  natural  dams,  and  the 
force  due  to  the  difference  in  level  can  be  seen  by  the 
energetic  way  in  which  the  water  squirts  through  the 
interstices  in  the  lock  gates,  when  the  river  is  a  navigable 
one.  A  huge  dam,  such  as  the  one  we  are  now  con- 
sidering, is  in  fact  merely  a  repetition  on  a  very  large 
scale  of  the  mill-dam  which  is  to  be  seen  on  most  of 
the  rivers  of  England,  where  the  old-fashioned  water- 
wheels  are  in  use.  The  "  mill-pond "  is  the  widened 


Sources  of  Power 

part  of  the  river  due  to  the  raising  of  the  water  level 
by  the  dam  ;  the  lt  mill-stream  "  is  simply  the  conduit 
which  leads  the  water  from  the  higher  level  to  the 
wheel,  over  which  it  falls,  into  the  water  at  the  level 
of  the  lower  side  of  the  dam. 

Instead  of  a  water-wheel,  however,  in  modern  plants 
a  "  water  turbine  "  is  used  ;  and  instead  of  taking  the 
water  round  a  mill-stream,  which  in  some  of  the  old 
mills  is  of  considerable  length,  the  turbines  are  placed 
near  to  or  actually  in  the  dam  itself,  so  that  the  water 
simply  rushes  through  tunnels  or  pipes  from  the  higher 
to  the  lower  side,  turning  the  turbines  as  it  goes. 

In  this  case  there  are  ten  turbines,  placed  in  pits 
formed  in  the  thickness  of  the  dam  itself,  at  one  end. 
Each  turbine  consists  of  two  wheels  fixed  to  a  vertical 
shaft,  which  comes  up  to  the  top  of  the  pit,  and  is  there 
connected  to  an  alternating-current  dynamo.  These 
are  different  from  ordinary  dynamos  inasmuch  as 
they  lie  upon  their  sides  and  rotate  upon  a  vertical  axis 
instead  of  on  a  horizontal  axis,  as  is  usually  the  case. 
They  can  thus  be  connected  directly  to  the  shafts  of 
the  turbines,  whereas  ordinary  upright  dynamos  would 
need  to  have  gearing  in  order  to  change  the  direction 
of  the  shafts. 

The  arrangement  can  be  easily  seen  from  the  draw- 
ing (Fig.  10),  which  is  a  section  through  the  dam  just 
where  one  of  the  turbines  occurs.  The  water  enters  a 
chamber  on  the  right,  through  submerged  arches,  in 
order  that  ice  or  anything  else  floating  on  the  surface 
may  be  kept  out  of  the  machinery.  There  it  encounters 
an  iron  grating  or  screen,  a  further  precaution  against 
solid  matter  entering  and  jamming  in  the  turbines  ; 
after  that  it  passes  down  the  intake  pipe,  part  goes 
through  each  of  the  wheels,  and  then  through  the  draft 
tubes  into  the  "  tail  race,"  as  the  channel  is  termed  into 
which  the  water  is  discharged  on  the  lower  side.  The 

68 


Sources  of  Power 

flow  of  water  through  the  turbine  can  be  regulated  by 
an  adjustable  door  at  the  mouth  of  the  intake  pipe. 
All  these  pipes,  and  the  turbine  pits  as  well,  are  simply 
openings  in  the  solid  block  of  concrete. 

The  turbine  wheels  themselves  are  cast  iron  wheels, 
in  which  are  arranged  a  number  of  buckets  or  vanes 
which  the  rushing  water  pushes  round  on  much  the 


FIG.  10. — Section  (simplified)  showing  how  the  Turbines  are 
placed  in  the  solid  mass  of  concrete. 

same  principle  as  a  windmill  is  pushed  round  by  the 
wind  rushing  past  its  sails.  The  arrangement  of  vanes 
is,  however,  more  complicated  than  the  sails  of  a  wind- 
mill, because  the  water  does  not  pass  straight  through ; 
it  first  enters  from  all  around,  passing  towards  the 
centre,  and  then  flows  downwards.  There  are,  therefore, 
two  sets  of  vanes,  one  of  which  is  acted  upon  by  the 
inward  movement  of  the  water  and  the  other  by  its 
subsequent  downward  movement.  Turbines  which 
work  by  the  inward  movement  only  are  called  (<  radial- 


Sources  of  Power 

flow  "  turbines,  since  the  water  flows  in  the  direction 
of  the  radii,  in  other  words  towards  the  centre.  Others, 
which  are  worked  by  the  downward  movement  only, 
are  called  "  parallel-flow  "  turbines,  since  the  flow  of 
water  is  parallel  with  the  axis  ;  while  those  which 
use  both,  as  just  described,  are  called  "  mixed-flow " 
turbines. 

The  dynamos  are,  of  course,  enclosed  in  a  building 
known  as  the  power-house,  which  is  situated  upon  the 
top  of  the  dam.  It  contains  an  overhead  crane  capable 
of  lifting  the  heaviest  part  of  the  turbines  or  dynamos, 
for  convenience  in  placing  them  in  position,  or  in  case 
they  need  to  be  taken  to  pieces  at  any  time.  Each  pair 
of  turbine  wheels,  by  the  way,  with  the  shaft  and  the 
rotating  part  of  the  dynamo,  together  weigh  about 
150  tons. 

Mention  was  made  just  now  of  the  danger  of  floating 
ice  getting  into  the  machinery.  Ice  is,  in  fact,  one  of 
the  great  troubles  with  a  plant  like  this,  and  the  whole 
scheme  has  been  devised  so  that,  as  far  as  possible,  all 
ice  shall  naturally  float  to  the  other  end  of  the  dam, 
away  from  the  power-house.  There  are  fenders,  too, 
formed  of  floating  logs,  and  also  the  submerged  arches 
noticed  just  now.  Still,  ice  might,  under  certain  cir- 
cumstances, evade  all  these  obstacles,  so  t(  chutes  "  are 
provided  at  certain  points,  openings  in  the  dam  through 
which  water  rushes,  and  over  which  lumps  of  ice  would 
be  carried  without  their  doing  harm  by  passing  through 
the  machinery. 

Altogether,  this  wonderful  undertaking  may  be  re- 
garded as  the  most  up-to-date  example  of  this  particular 
type  of  installation,  and  probably  it  will  remain  so  for 
many  years  to  come. 

It  only  represents,  however,  one  kind  of  water-power 
plant  ;  that  in  which  a  low  fall  is  used.  In  some 
favoured  localities  a  mountain  lake  or  stream  can  be 

70 


Sources  of  Power 

tapped  at  a  high  level,  and  the  water  brought  down  in 
pipes  at  a  great  pressure. 

There  is  an  installation  of  this  description  in  Switzer- 
land, where  the  water  is  drawn  from  a  lake  over  3000 
feet  above  the  power-station.  Consequently  the  water 
has  a  pressure  at  the  latter  point  of  1300  Ibs.  per 
square  inch,  and  it  is  quite  evident  that  a  small  jet  at 
that  pressure  will  have  as  much  force  in  it  as  a  large 
volume  of  water  at  McCall's  Ferry.  The  motor  generally 
used  under  these  conditions  is  therefore  quite  different 
from  the  one  just  described.  It  is  known  as  the  "  Pelton 
wheel/'  and  consists  of  a  large  wheel,  fixed  on  a  hori- 
zontal shaft,  and  having  a  large  number  of  metal  cups 
attached  to  its  circumference.  The  water  issues  in  the 
form  of  a  jet  from  a  nozzle,  and  strikes  against  the 
inside  of  the  cups,  thereby  driving  the  wheel  round ;  a 
very  simple  machine  in  its  general  ideas,  but  a  very 
efficient  one  under  these  conditions.  Its  speed  is  regu- 
lated by  deflecting  the  nozzle  upwards  so  that  part  of 
the  jet  misses  the  cups  altogether. 

Before  leaving  the  subject,  reference  may  be  made 
to  a  source  of  water-power  which  is  not  much  used, 
although  it  seems  possible  that,  some  day,  a  satisfactory 
method  may  be  found  of  turning  it  to  account — the  rise 
and  fall  of  the  tide. 

One  of  the  first  patents  recorded  at  the  British  Patent 
Office,  and  dated  in  the  reign  of  James  I.,  granted 
a  monopoly  for  the  establishment  of  floating  mills  in 
harbours  and  estuaries,  and  there  seems  little  doubt  that 
the  idea  was  to  use  the  force  of  the  tide  to  work  them. 
There  are  such  mills  in  some  parts  of  Europe  to-day  ; 
they  may  be  described  as  like  paddle  ships,  only,  instead 
of  machinery  in  the  ships  turning  the  paddles,  the 
paddles  turn  the  machinery.  The  vessel  is  anchored  in 
a  tidal  creek  or  river,  and  the  water,  flowing  past,  turns 
the  wheels.  Unfortunately,  however,  the  velocity  of 

71 


Sources  of  Power 

the  tidal  current  is  not  sufficient  to  develop  much 
power  by  this  means. 

Many  people  have  meditated  upon  the  possibility  of 
anchoring  an  old  ship  at  some  convenient  spot,  and  in 
some  way  making  its  rise  and  fall  on  the  tide  do  useful 
work,  but  when  analysed  the  amount  of  power  so 
obtained  would,  even  if  it  could  be  done  conveniently, 
be  ridiculously  little.  For  suppose  it  were  a  vessel 
with  a  buoyancy  of  1000  tons,  and  that  it  was  anchored 
at  a  spot  when  the  rise  and  fall  was  say  30  feet ;  the 
amount  of  work  done  in  twelve  hours  would  be  1000 
tons  lifted  30  feet, or  67,200,000  foot  pounds — seemingly 
a  huge  figure.  It  only  represents,  however,  what  a  five- 
horse-power  gas-engine,  with  suction  producer,  would 
do  easily  for  about  a  shilling.  This  is  an  illustration  of 
how  a  promising-looking  idea  often  fades  away  to  nothing 
when  critically  examined. 

The  best  scheme  of  all — one,  in  fact,  which  is  actually 
in  operation  in  a  few  places — is  this.  Across  the  mouth 
of  a  tidal  creek  a  dam  is  built.  In  it  are  a  pair  of 
lock  gates  which  open  inwards  so  as  to  form  a  large 
"  non-return  "  valve ;  they  will  open  and  let  the  water 
in  freely,  but  close  as  soon  as  it  attempts  to  return. 
Thus  the  creek  behind  the  dam  forms  a  large  lake  or 
reservoir  which  is  filled  every  tide,  and  when  the  tide 
turns  the  water  can  be  allowed  to  run  out  again  over  a 
water-wheel. 

As  far  as  the  writer  is  able  to  ascertain,  this  plan  has 
not  been  tried  with  a  modern  turbine,  but  only  with  an 
old-fashioned,  inefficient  water-wheel.  It  is  just  possible 
that  under  very  favourable  natural  conditions — that  is,  a 
large  creek  with  a  very  narrow  opening  and  a  very 
great  tidal  movement — it  might  be  a  success,  and  there 
seems  no  reason  why  the  water  should  not  be  made  to 
work  the  turbine  as  it  flows  in  as  well  as  coming  out  of 
the  reservoir. 

72 


Sources  of  Power 

The  real  difficulty  would  appear  to  lie  where,  perhaps, 
the  non-technical  reader  would  least  suspect  it.  The 
water  passing  in  will  carry  a  certain  amount  of  mud 
and  sand  with  it,  which  it  will  deposit  in  the  reservoir, 
and  the  cost  of  removing  this  periodically  will  probably 
be  sufficient  to  make  the  plan  an  expensive  one. 


73 


CHAPTER  V 

HOW  POWER   IS   CARRIED 

WHEN  in  an  earlier  chapter  I  enumerated  the  sources 
of  power  as  wind,  water,  and  heat,  it  may  have  sur- 
prised some  readers  to  see  no  mention  of  electricity. 
We  are  so  accustomed  to  speak  of  trains,  trams,  and 
machinery  as  being  "  driven  by  electricity "  that  we 
often  forget  that  it  is  not  a  source  of  power,  but  simply 
a  means  of  conveying  power  from  one  place  to  another. 

This,  perhaps,  needs  a  slight  qualification. 

When  generated  by  means  of  chemical  batteries, 
such  as  we  use  to  work  telegraphs  and  electric  bells, 
electricity  may  be  ranked  among  the  "prime  movers," 
but  the  quantity  that  can  be  produced  in  that  way  is  so 
small  and  so  limited  in  its  uses  that  the  statement  just 
made  is  for  practical  purposes  quite  accurate. 

We  need  only  think  of  the  fact  that  no  one  has  ever 
seen  a  dynamo  giving  out  current  by  itself,  to  realise 
this.  It  needs  some  other  force,  one  of  the  three 
already  enumerated,  to  drive  it,  and  then  it  produces 
the  current  of  electricity  which  may  be  used  in  such 
marvellous  ways  to  drive  machinery  perhaps  many 
miles  away. 

It  is  as  a  means  of  transmitting  power,  therefore, 
that  electricity  is  of  so  much  service  to  the  engineer. 
It  has  in  this  way  worked  changes  which  are  little 
short  of  miraculous. 

There  is  no  better  instance  of  this  than  the  modern 
electric  tramcar.  It  possesses  possibilities  of  usefulness 

74 


How  Power  is  Carried 

so  much  in  advance  of  the  old  horse-drawn  car  as  to 
make  it  really  a  new  invention,  and  its  existence  is 
entirely  due  to  the  convenient  way  in  which  electricity 
can  convey  the  power  generated  by  large  engines  at 
the  generating  station  to  the  cars  upon  the  road. 

The  "  tube "  railways,  too,  which  are  such  a  boon 
to  Londoners,  are  unthinkable  apart  from  the  use  of 
electricity  to  drive  the  trains.  Moreover,  in  some  parts 
of  the  world  there  are  vast  stores  of  power,  in  the 
shape  of  waterfalls,  running  to  waste  because  they  are 
too  far  from  the  centres  of  population,  where  the 
energy  is  required.  Here  electricity  steps  in,  and  forms 
a  means  by  which  this  force  can  be  conveyed  many 
miles  to  some  place  where  it  will  be  useful.  An 
instance  of  this  was  described  in  the  last  chapter. 

In  modern  factories,  too,  it  is  the  practice  to  make 
use  of  electricity  for  turning  the  machines.  Where 
there  used  to  be  many  leather  belts  and  long  lines  of 
revolving  shafts  there  are  now  motors,  sometimes  one 
for  each  machine,  and  sometimes  one  for  each  small 
group  of  machines.  In  the  old  days  it  was  no  un- 
common thing  for  30  per  cent  of  the  power  of  the 
engine  to  be  taken  up  in  simply  turning  round  the 
shafting,  without  working  a  single  machine.  How 
serious  a  loss  this  was  hardly  needs  pointing  out.  Sup- 
posing, too,  that  there  was  some  small  job  which  had 
to  be  finished  after  the  ordinary  working  hours,  the 
whole  of  that  shafting  had  to  be  kept  in  revolution  for 
the  sake,  perhaps,  of  one  small  machine. 

The  electric  motor  has  altered  all  this,  for  among 
other  very  valuable  qualities  it  has  this  one :  it  re- 
solutely refuses  to  take  in  more  current  than  it  needs 
to  do  the  work  in  hand.  If  it  has  a  light  job  to  do  it 
takes  little  current,  and  as  the  load  upon  it  increases  it 
takes  just  enough  extra  current  to  enable  it  to  do  its 
work  and  no  more.  This,  too,  is  an  inherent  virtue  in 

75 


How  Power  is  Carried 

the  machine;  and  is  not  the  result  of  any  regulating 
device. 

Thus,  if  only  one  machine  is  at  work  in  a  factory,  the 
engine  and  dynamo  are  only  called  upon  to  supply  the 
tiny  quantity  of  current  needed  for  that  one  machine, 
and  no  more. 

Electricity  is  one  of  nature's  mysteries.  We  have 
not  the  faintest  idea  what  it  is.  We  are  able  to  form 
an  idea  as  to  how  a  current  of  electricity  is  formed  ;  it 
seems  to  be  a  commotion  among  the  electrons,  the  tiny 
particles,  of  which,  science  tells  us,  all  matter  is  built 
up.  We  may  go  so  far  as  to  say  that  these  electrons 
are  electricity,  but  that  does  not  help  us  much,  since  we 
cannot  say  what  the  electrons  are.  They  are  almost 
infinitely  minute.  Their  size  is  for  smallness  as  much 
beyond  our  powers  of  comprehension  as  the  distance 
of  the  stars  is  for  magnitude.  Still  there  is  direct 
evidence  of  their  existence,  and  there  seems  no  reason 
to  doubt  that  it  is  a  movement  among  these,  communi- 
cated from  one  atom  to  another  along  a  long  line,  which 
accounts  for  what  we  are  accustomed  to  call  a  current 
of  electricity. 

That  is  enough,  however,  as  regards  pure  theory.1 
The  engineer  is  most  concerned  with  the  practical 
application  of  scientific  phenomena  to  the  service  of 
mankind.  He  only  troubles  about  the  theories  in  so 
far  as  they  help  him  to  understand  and  make  better 
use  of  the  phenomena.  So,  since,  without  knowing 
what  it  is,  we  are  able  to  turn  electricity  to  many  useful 
purposes,  we  will  leave  the  theories  and  come  to  the 
practical  applications. 

Of  all  the  wonderful  things  that  have  been  observed 
in  connection  with  electricity  there  is  one  which  for 
practical  purposes  is  of  more  importance  than  any 

1  Readers  who  would  like  to  know  more  about  this  are  referred  to  Scientific 
Ideas  of  To-day. 

76 


By  permission  of 


Messrs.  Wellman,  Seaver,  &•  Head,  Ltd. 


AN  ELECTRO-MAGNET  ATTACHED  TO  A  CRANE  FOR  LIFTING 
PIG-IRON 

The  moment  the  current  is  stopped  the  pigs  will  drop  off.     The  smaller  picture 
represents  a  similar  magnet  lifting  wooden  kegs  full  of  iron  nails. 


How  Power  is  Carried 

other.  It  is  this.  When  electricity  is  flowing  through 
a  wire  or  any  other  conductor  it  exercises  a  mysterious 
influence  all  around.  If  the  current  is  strong  enough 
it  will  move  a  piece  of  iron  or  it  will  cause  agitation  in 
the  needle  of  a  mariner's  compass.  It  does  not  need 
to  touch  these  things,  but  can  exercise  this  force  or 
influence  at  a  considerable  distance.  This  strange 
influence,  as  inexplicable  as  electricity  itself,  we  call 
magnetism. 

Nor  have  we  yet  exhausted  the  wonders  of  this 
phenomenon,  for  just  as  a  current  in  a  wire  turns  the 
wire  into  a  magnet  so  the  move- 
ment of  a  magnet  in  the  neigh- 
bourhood of  a  wire  will  cause 
a  current  to  flow  along  it,  or, 
as  it  is  usually  expressed,  will 
"induce"  a  current  in  it. 

In  these  two  facts,  then — that 
electricity  can  produce  magne- 
tism and  that  magnetism  can 

produce  electricity  —  we  have  FIG.  n.— The  essential  parts 
the  secret  of  the  dynamo.  It 
is,  in  the  principles  of  its  con- 
struction, a  remarkably  simple 
machine.  There  is  a  part  which  remains  still,  called 
the  field  magnet,  an  iron  frame-like  structure  wound 
over  and  over  in  certain  parts  with  wire  enclosed  in  an 
insulating  covering.  Through  this  wire  a  current  of 
electricity  passes,  and  so  the  whole  structure  is  made 
into  a  powerful  magnet.  Then  inside  this  frame  there 
turns  another  part  called  the  armature.  This  is  also  of 
iron,  and  upon  it  too  are  wound  layers  of  insulated 
wire. 

When  the  armature  is  turned  rapidly  round  by  an 
engine  or  some  other  suitable  power,  the  movement  of 
the  wires  on  the  armature  in  the  neighbourhood  of  the 

77 


of  a  Dynamo.  The  shaded 
part  revolves.  The  other 
part  remains  still. 


How  Power  is  Carried 

field  magnets  causes  currents  to  be  induced  in  them. 
These  currents  flow  to  a  part  called  the  commutator, 
which  is  fixed  upon  the  same  shaft  as  the  armature 
and  which  turns  with  it.  Two  or  more  small  arms,  or 
brushes  as  they  are  called,  are  placed  with  their  ends  in 
contact  with  the  commutator,  and  these  collect  the 
current,  which  can  then  be  led  away 'along  wires  to  any 
place  where  it  is  needed. 

But  there  are  two  kinds  of  dynamos.  The  one  just 
described  generates  tl  direct "  or  "  continuous  "  current 
while  the  other  generates  "  alternating "  current,  and 
before  it  is  possible  to  make  clear  the  difference  between 
the  two  it  will  be  necessary  to  explain  these  terms. 

Instead  of  electricity  passing  along  a  wire  just  imagine 
for  a  moment  water  flowing  along  a  pipe.  It  is  easy 
to  conceive  a  constant  stream  of  water  being  pumped 
along  the  pipe  by  an  engine  and  used  to  drive  a  water 
motor  at  the  further  end.  That  would  be  a  continuous 
current.  But  suppose  that  instead  of  a  constant  stream 
the  engine  pushed  the  water  in  the  pipe  to  and  fro — a 
few  inches  one  way  and  then  a  few  inches  back  in  the 
opposite  direction — the  force  would  still  be  communi- 
cated to  the  further  end  of  the  pipe,  and  a  suitably 
designed  motor  could  be  driven  by  it,  but  it  would  be 
a  totally  different  sort  of  current  from  the  constant 
stream  of  water  always  in  the  same  direction. 

That  illustrates  for  us,  in  a  rough  approximate  sort 
of  way,  the  difference  between  the  direct  current  and 
the  alternating  current  of  electricity. 

The  direction  in  which  the  induced  current  flows 
along  a  wire  depends  upon  the  direction  in  which  the 
wire  moves  in  relation  to  the  magnets.  If  the  direction 
of  movement  be  reversed  the  direction  of  the  current 
will  be  reversed  also. 

Now  any  point  upon  a  revolving  body  (except,  of 
course,  its  centre)  is  continually  passing  first  one  way 

78 


How  Power  is  Carried 

and  then  the  other,  up  and  then  down,  or  to  the  right 
and  then  to  the  left,  just  whichever  way  you  look  at  it, 
one  way  one  half  the  revolution  and  the  other  way  the 
other  half.  This  applies  of  necessity  to  the  wires  on 
the  armature  as  it  revolves,  and  thus  the  currents  in- 
duced in  them  are  alternately  first  in  one  direction  and 
then  in  the  other — that  is  to  say,  they  are  alternating 
currents.  In  the  direct-current  dynamo  as  just  de- 
scribed this  is  corrected  by  the  action  of  the  commu- 
tator, which  consists  of  a  number  of  segments  insulated 
from  one  another,  which  make  contact  with  the  brushes 
in  succession.  A  brush  is  only  in  contact  with  a  seg- 
ment during  the  time  that  current  is  being  generated 
in  one  direction.  The  moment  the  direction  in  any  of 
the  wires  begins  to  change,  the  segment  to  which  those 
particular  wires  are  connected  passes  under  the  other 
brush. 

An  alternating-current  dynamo,  however,  has  no 
commutator,  but  instead  simply  two  insulated  metal 
rings,  against  which  the  brushes  slide  continually,  so 
that  the  alternations  of  the  current  are  unchanged. 
There  is  another  difference  between  the  two  machines, 
and  that  is  that  in  the  alternator  it  is  generally  the  field 
magnets  which  go  round  and  the  armature  which  stands 
still.  There  is  no  principle  involved  in  this,  however  ; 
it  is  simply  a  matter  of  convenience. 

The  difference  between  the  two  kinds  of  dynamo  can 
therefore  be  put  briefly  in  this  way.  In  an  alternator 
the  natural  alternations  of  the  current  are  not  changed, 
but  in  the  direct-current  machine  there  is  a  commutator 
which  turns  them  into  a  continuous  stream. 

This  naturally  brings  the  question,  What  are  the 
advantages  of  the  two  types  ?  We  will  come  to  that 
in  a  moment. 

We  measure  a  supply  of  water  in  two  ways.  We 
say  there  is  a  flow  of  so  many  gallons  per  hour  and 

79 


How  Power  is  Carried 

a  pressure  of  so  many  pounds  per  square  inch.  In 
just  the  same  way  a  current  of  electricity  can  be 
described  as  having  a  strength  of  so  many  "  amperes," 
which  is  the  equivalent  of  gallons  per  hour,  and  a 
pressure  of  so  many  "volts,"  which  is  analogous  to 
pounds  per  square  inch.  It  is  not  necessary  to  go 
into  the  exact  value  of  these  units  of  electrical  measure- 
ment, but  it  will  be  interesting,  perhaps,  to  state  that 
the  current  given  off  by  the  familiar  dry  cell  such  as  is 
often  used  for  electric  bells  is  at  a  pressure  of  a  little 
over  one  volt. 

There  is  another  electrical  measurement  which  we 
often  use  in  conjunction  with  these  two,  and  that  is 
the  "  ohm."  It  is  used  to  measure  the  resistance  which 
a  wire  offers  to  the  passage  of  a  current  along  it.  A 
copper  wire  1000  yds.  long  and  -^  in.  in  diameter  has 
a  resistance  of  about  eight  ohms. 

An  ampere  is  the  strength  of  the  current  which 
a  force  of  one  volt  will  cause  to  flow  along  a  wire 
having  a  resistance  of  one  ohm.  Thus,  it  will  be  seen, 
these  three  measures  are  all  related  to  one  another. 

If  we  were  transmitting  power  by  water  through 
a  pipe  we  could  use  a  lot  of  water  at  a  low  pressure  or 
a  very  little  water  at  a  high  pressure.  So  long  as  the 
machine  which  it  worked  at  the  further  end  were  made 
to  suit,  it  would  not  matter  which  of  these  we  did, 
except  for  one  consideration :  the  pipes  would  have  to 
be  in  proportion  to  the  quantity.  By  using  the  small 
quantity  at  a  high  pressure  we  could  do  with  much 
smaller  pipes,  and  the  saving  in  cost  if  the  line  of  pipes 
were  a  long  one  would  be  considerable.  If  they  had 
to  be  made  of  an  expensive  substance  like  copper,  the 
difference  would  be  very  great  indeed. 

But  the  lt  pipes "  used  for  transmitting  power  by 
electricity  are  solid  wires  made  of  this  costly  metal,  and 
so  if  the  distance  be  considerable  the  current  is  always 

80 


mll 

rt    •  ^S  «  „ 


B;IIJJI 


0    ~'J 

O    ^  t 


wliiiil 

O  «  3  ««C  c 


8t 


oUa^jj'-M 

•"  rt  2  S.S  S?.S 

w ,y, vS  rrirj.S  > 


How  Power  is  Carried 

generated  and  transmitted  at  a  very  high  voltage,  in 
order  that  the  quantity,  and  consequently  the  size  of 
the  wires,  may  be  kept  down  to  the  minimum. 

Now  at  a  high  voltage  a  commutator  is  a  nuisance. 
As  a  segment  recedes  from  under  a  brush  the  electricity 
leaps  across  the  space  from  one  to  the  other,  causing 
great  heat  and  doing  damage  to  both.  The  same 
difficulty  does  not  occur  with  the  slip  rings  on  an 
alternator,  since  the  brushes  never  leave  them,  and  in 
most  cases  it  is  only  the  moderately  powerful  "  exciting  " 
current  for  the  field  magnets  which  passes  through  them, 
and  so  for  generating  high  voltages  the  alternator  is 
invariably  the  machine  used. 

A  concrete  illustration  of  this  will  make  it  quite  easy 
to  understand.  In  the  case  of  the  London  Under- 
ground Railways  the  current  is  generated  at  Chelsea  at 
a  pressure  of  11,000  volts,  and  of  course  it  is  alternat- 
ing current.  From  there  it  passes  to  the  sub-stations 
placed  at  intervals  along  the  system,  where  it  first  of  all 
goes  to  the  transformers.  These  are  simply  huge 
induction  coils.  Most  of  us  have  played  with  induction 
coils  at  some  time  or  other.  They  are  often  called 
shocking  coils,  because  they  are  used  to  give  people 
electric  shocks.  They  consist  of  two  coils  of  wire,  one 
inside  the  other,  and  if  a  current  of  low  voltage  is  sent 
through  one  of  them,  a  current  of  higher  voltage  (but  of 
proportionately  reduced  quantity)  will  come  out  of  the 
other.  They  are  usually  worked  by  a  single  chemical 
cell,  the  current  from  which  we  are  ordinarily  unable 
to  feel/ but  which  in  its  intensified  form  we  feel  some- 
times more  than  we  like. 

The  difference  between  the  current  which  goes  in 
and  that  which  comes  out  is  due  to  the  difference  in  the 
number  of  turns  of  wire  in  the  two  coils,  and  it  will  work 
equally  well  the  opposite  way — that  is  to  say,  we  can 
arange  such  a  coil  so  that,  if  fed  with  a  small  current 

81  F 


How  Power  is  Carried 

of  high  voltage,  it  .will  give  out  another  current  at  a  much 
lower  voltage  but  immensely  increased  in  volume. 

That,  then,  is  what  takes  place  in  the  transformers  in 
the  sub-stations.  Current  at  11,000  volts  is  fed  into 
them,  and  a  much  greater  current  at  500  volts  comes 
out.  Now  500  volts  is  a  suitable  pressure  for  working 
the  motors  on  the  trains,  but  the  current  is  still 
alternating,  whereas  the  motors  used  need  direct 
current,  so  it  passes  from  the  transformers  to  machines 
called  converters.  These  are  practically  a  direct- 
current  dynamo  and  an  alternator  combined  into  one 
machine,  and  the  current  which  goes  in  alternating 
comes  out  continuous.  The  converter  automatically 
sorts  out  the  little  puffs  of  current  which  constitute  the 
alternating  current,  puts  them  all  the  same  way  about, 
and  delivers  them  all  in  one  continuous  stream. 

From  the  converters  the  electricity  passes  to  the 
conductor  rails,  which  take  it  to  the  motors  on  the 
trains. 

As  we  are  concerned,  in  this  chapter,  with  the 
transmission  of  power  by  electricity,  and  shall  be 
dealing  with  traction  in  a  future  one,  we  will  not 
pursue  the  course  of  the  current  any  further.  We 
have  seen,  however,  how  it  was  generated  at  a  high 
voltage  so  that  it  could  be  conveyed  by  small  cables, 
and  how  it  was  transformed  into  a  lower  voltage  for 
use,  and  finally  converted  into  continuous  current  as  re- 
quired by  the  motors.  And  now  we  shall  see  where  the 
continuous-current  dynamo  scores  over  the  alternator. 

The  arrangement  which  we  have  just  been  looking 
at  shows  how  cost  was  saved  in  the  copper  conductors, 
but  from  that  saving  must  be  deducted  the  cost  of  the 
sub-stations  and  the  transformers  and  converters.  We 
can  easily  see,  then,  that  if  the  current  has  not  to  be 
conveyed  very  far  it  is  cheapest  to  generate  direct 
current  to  start  with  at  about  the  voltage  that  we  need, 

82 


How  Power  is  Carried 

and  so  save  the  use  of  converters  and  transformers 
altogether. 

Speaking  generally,  then,  we  may  say  that  alternating- 
current  dynamos  are  used  when  a  high  voltage  is 
needed  for  transmission  to  a  long  distance  and  direct- 
current  dynamos  for  generating  low  voltage  currents 
for  use  near  at  hand. 

Readers  may  sometimes  be  puzzled  by  hearing 
alternating  current  spoken  of  as  "  single-phase,"  "  two- 
phase,"  or  "  three-phase,"  terms  which  may  conveniently 
be  explained  at  this  point. 

In  some  alternators,  the  conductors  on  the  armature, 
in  which  the  current  is  induced,  are  all  arranged 
together,  so  that  the  current  flows,  first  one  way  and 
then  the  other,  in  them  all  simultaneously.  That  is 
a  "  single-phase  "  machine,  and  produces  "  single-phase  " 
current. 

In  others  these  conductors  are  grouped  in  two  sets, 
so  arranged  that  the  current  induced  in  one  set  is 
flowing  at  its  maximum  strength  just  as  that  in  the 
other  set  is  changing  its  direction  and  is  consequently 
not  flowing  at  all.  Such  are  called  "two-phase" 
machines,  and  produce  " two-phase"  current,  as  it 
is  called — in  reality,  two  separate  currents,  each  flowing 
in  a  separate  pair  of  wires. 

A  "  three-phase  "  machine,  in  like  manner,  has  three 
sets  of  conductors,  and  produces  three  separate  currents, 
the  alternations  in  which  succeed  each  other  at  equal 
intervals.  These  three  separate  currents  are  spoken 
of  collectively  as  "  three-phase "  current,  and  it  must 
be  noted  that  they  do  not  require  six  separate  wires 
as  might  be  expected,  but  only  three,  for  the  relative 
times  of  the  alternations  are  such  that  at  any  moment 
the  current  in  two  of  them  is  equal  in  volume  to  that 
in  the  third,  and  opposite  in  direction,  so  that  each 
wire  in  turn  acts  as  the  "  return  "  wire  to  the  other  two. 

83 


How  Power  is  Carried 

Now  we  can  take  a  look  at  the  motors  which  turn 
the  electricity  back  into  mechanical  power  when  it 
gets  to  the  end  of  its  journey. 

The  direct-current  motor  is  a  beautiful  machine.  It 
is  small,  quiet,  easy  to  control,  starts  itself  readily,  is 
easily  reversible,  and  is  efficient  into  the  bargain.  We 
have  seen  how  on  the  underground  railways  the 
expense  was  incurred  of  turning  the  current  from 
alternating  into  direct.  That  was  simply  in  order  to 
secure  the  advantages  of  the  direct-current  motor. 
Were  it  not  for  this,  direct  current  would  probably  go 
out  of  use  altogether,  except  for  such  work  as  electro- 
plating, for  which  alternating  current  is  no  use  at  all. 

This  valuable  machine  is  exactly  the  same  in  con- 
struction as  a  direct-current  dynamo  ;  in  fact  one 
machine  can  be  used  for  both  purposes.  The  reason 
for  this  can  be  easily  explained.  Every  magnet  has 
two  ends,  and  there  is  a  mysterious  difference  between 
them.  If  a  magnet  be  suspended  so  that  it  can  swing 
round  freely,  one  end  will  turn  to  the  north  and  the 
other  to  the  south.  These  two  ends  are  therefore 
called  the  north  and  south  poles  of  the  magnet. 
Now  if  two  magnets  are  placed  near  together  with 
their  like  poles  (that  is  to  say,  the  two  north  or  the 
two  south)  touching,  they  will  repel  each  other,  but  if 
a  north  and  a  south  be  brought  together  they  will 
attract  each  other.  We  may  put  it  briefly  ;  unlike 
poles  attract,  like  poles  repel. 

Now  just  as  the  direction  of  movement  of  the  wire 
in  relation  to  the  magnet  determines  the  direction  of 
the  induced  current,  so  the  direction  of  the  current 
determines  the  polarity  of  the  magnet.  If  you  had 
an  electro  magnet  and  found  that  one  particular  end 
was  a  north  pole  you  might  know  for  a  certainty 
that  if  you  reversed  the  direction  of  the  current  it 
would  become  a  south  pole. 


How  Power  is  Carried 

These  two  facts,  taken  together,  explain  why  the 
armature  of  a  dynamo  will  turn  round  if  current  be 
fed  into  it  and  so  become  converted  into  a  motor. 
When  the  current  commences  to  flow  the  armature 
becomes  a  magnet,  and  its  poles  are  attracted  or  re- 
pelled, as  the  case  may  be,  by  the  field  magnet,  the 
result  being  that  it  is  forced  round. 

This  is  one  of  those  matters  in  which  a  diagram  will 
explain  easily  what  mere  words  would  never  be  able  to 
make  clear  at  all. 

Fig.  1 2  is  a  diagram  showing  the  two  essential  parts 
of  a  motor.  The  field  magnet,  when  made  in  that 


FIGS.  12  and  13. — Diagrams  showing  the  working  of  a  Direct-current  Motor. 

form,  has  four  poles,  two  of  which  will  be  north  and 
two  south.  We  will  assume  that  they  are  as  marked, 
N.  meaning  north  and  S.  south. 

The  armature,  too,  although  it  is  round,  is  so  wound 
with  wire  and  so  fed  with  current  that  it  also  is  a 
magnet  with  four  poles,  and  we  will  assume  that  it  is  in 
the  position  shown.  Then  we  can  easily  see  that,  as 
soon  as  the  current  begins  to  flow,  the  armature  will 
be  forced  round  in  the  direction  of  the  arrow. 

But  we  are  then  confronted  with  this  difficulty.  As 
soon  as  the  armature  reaches  the  position  shown  in 
Fig.  13  it  will  stop,  as  the  unlike  pairs  of  poles  are 
then  as  near  together  as  they  can  be,  and  any  further 

85 


How  Power  is  Carried 

movement  will  tend  to  separate  them,  which  of  course 
the  magnetic  force  will  try  to  resist.  Fortunately, 
however,  we  can,  by  altering  the  course  of  the  current 
in  the  armature,  cause  its  poles  to  shift  backwards 
until  the  state  of  things  shown  in  our  first  diagram  is 
restored,  and  this  the  commutator  does  for  us  auto- 
matically. Just  at  the  moment,  then,  when  the  poles 
come  together,  the  poles  of  the  armature  move  back 
electrically  (for  it  must  be  clearly  understood  that  the 
armature  does  not  move  back,  it  is  only  the  magnetism 
which  takes  up  a  fresh  position  on  the  armature),  and 
so  the  magnetic  force  generated  by  the  electricity  sup- 
plied to  the  machine  causes  it  to  rotate  continuously. 

In  a  direct-current  motor,  current  is  supplied  to  the 
field  magnets  so  as  to  energise  them,  as  well  as  to  the 
armature.  In  the  motors  used  for  alternating  current 
the  electricity  is  supplied  only  to  the  field  magnets,  and 
since  it  is  alternating  it  has  the  effect  of  inducing  the 
necessary  current  in  the  rotating  part.  These  motors 
are  therefore  called  "  induction  motors."  They  are  not 
so  convenient  as  direct-current  motors,  since  except 
with  three-phase  current  they  do  not  reverse  them- 
selves, the  speed  cannot  be  regulated,  and  they  are  not 
so  reliable.  Still  it  is  so  convenient  to  have  motors 
that  will  work  with  alternating  current  that  they  are 
used  very  largely.  There  is  another  kind  of  alternating- 
current  motor  that  is  used  on  railway  trains,  but  that 
will  be  referred  to  in  the  chapter  on  electric  traction. 

Another  great  advantage  of  the  transmission  of 
power  by  electricity  is  that  it  enables  many  things  to 
be  done  by  power  which  would  be  impossible  without 
it.  It  has  been  suggested  that  it  may  even  result  in 
the  revival  of  home  industries.  It  would  be  in  many 
cases  impossible  for  a  home  worker,  such  as  a  weaver, 
for  instance,  to  have  a  steam-engine  or  even  a  gas- 
engine  in  his  house  to  drive  his  machine,  but  an 

86 


How  Power  is  Carried 

electric  motor  driven  off  the  public  mains  would  take 
up  very  little  room,  need  no  attention,  and  be  always 
ready  to  start. 

It  must  not  be  thought,  however,  that  in  factories 
electricity  has  entirely  done  away  with  the  use  of 
shafting,  pulleys,  and  belts.  On  the  other  hand,  the  use 
of  roller  bearings  has  given  the  latter  a  new  lease  of 
life.  It  used  to  be  the  invariable  practice  for  the 
shaft  simply  to  slide  round  in  a  bearing — that  is,  a  broad 
ring  of  metal  encircling  the  shaft,  in  which  it  was  free 
to  turn  easily.  Needless  to  say  this  caused  heavy 
losses  through  friction,  but  with  a  ring  of  rollers  instead 
of  the  solid  bearing  this  loss  is  very  largely  removed, 
and  it  is  claimed  in  some  cases  that  machinery  in  a 
large  workshop  can  be  more  cheaply  driven  by  shafting 
with  roller  bearings  than  it  can  by  electric  motors. 


CHAPTER   VI 

THE   ENGINEER'S   MATERIALS 
IRON    AND    STEEL 

IN  the  course  of  his  work  the  engineer  brings  into  use 
a  great  variety  of  materials,  but  there  is  one — iron — 
which  stands  far  above  all  others  in  importance.  In- 
deed it  would  be  no  exaggeration  to  say  that  without  it 
engineering  as  we  know  it  to-day  could  not  exist. 

The  use  of  iron  marked  one  of  the  stages  in  man's 
development,  so  that  one  period  of  the  world's  history 
is  known  as  the  "  iron  age."  This  was  no  doubt  due 
to  the  fact  that  iron  in  a  natural  state  is  practically 
unknown.  The  ores  in  which  it  is  contained  are  to  all 
appearance  simply  lumps  of  stone  bearing  not  the 
slightest  resemblance  to  the  metal,  and  so  it  would  of 
necessity  be  only  when  man  had  gained  a  certain 
amount  of  knowledge  that  he  would  discover  the 
metallic  treasures  hidden  in  the  rocks  around  him. 

The  ores  of  iron  are  mostly  either  oxides  or  car- 
bonates— that  is  to  say,  iron  in  combination  with 
oxygen  and  carbon.  Not  mere  mixtures,  be  it  ob- 
served, but  chemical  combinations,  which  means  to 
outward  appearance  different  substances  altogether. 
A  simple  illustration  of  such  a  combination  is  common 
rust,  which  is  oxide  of  iron — iron  in  combination  with 
oxygen — and  but  for  the  fact  that  we  have  been  in  the 
habit  of  seeing  it  form  on  iron,  and  so  have  come  to 
associate  the  two  in  our  minds,  we  should  never  dream 

88 


The  Engineer's  Materials 

that  there  was  any  connection  whatever  between  the 
dull  red  dust  and  the  bright,  tenacious  metal. 

Iron  ores  are  very  plentiful  in  many  parts  of  the 
world,  and  needless  to  say  the  quality  varies  consider- 
ably, so  that  different  combinations  can  be  used  to 
produce  different  classes  of  iron. 

When  the  ore  comes  from  the  mine  it  is  first  of  all 
roasted  in  a  furnace  to  drive  off  the  moisture,  after 
which  it  is  taken  to  the  blast-furnace.  This  is  a  huge 
vertical  cylinder,  often  90  or  100  feet  high,  built  up  of 
firebrick,  strengthened  with  iron.  The  fire  is  made  at 
the  bottom,  and  the  ore,  together  with  fresh  supplies  of 
fuel  to  keep  up  the  fire,  is  thrown  on  at  the  top. 
Around  the  lower  part  are  a  number  of  holes  through 
which  air  is  blown,  and  under  the  influence  of  the  air- 
blast,  intense  heat  is  developed.  The  effect  of  the  heat 
upon  the  ore  is  to  loosen  the  connection  between  the  iron 
and  oxygen,  or  iron  and  carbon,  as  the  case  may  be,  and 
so  allow  the  iron  to  get  free.  At  the  extreme  bottom 
of  the  furnace  there  is  a  hole  which  is  normally  closed 
by  a  plug,  and  when  sufficient  molten  iron  has  accumu- 
lated in  the  furnace  this  plug  is  removed  and  the  metal 
allowed  to  run  out. 

At  the  same  time  that  the  ore  and  coal  (or  coke)  are 
thrown  in,  quantities  of  limestone  are  put  in  too.  This 
combines  with  certain  earthy  impurities  in  the  ore,  and 
forms  a  thick  liquid  called  slag,  which  floats  on  the 
top  of  the  iron,  and  is  allowed  at  intervals  to  run  out 
through  another  hole  higher  up  in  the  furnace.  It  is 
this  slag,  after  it  has  cooled  and  solidified,  which  consti- 
tuted those  enormous  mounds  which  were  at  one  time 
such  a  conspicuous  feature  in  the  iron-producing  dis- 
tricts, and  are  so  now,  indeed,  in  many  places.  There 
used  to  be  no  way  of  getting  rid  of  it,  and  so  in  the 
course  of  years  veritable  mountains  of  it  accumulated, 
but  now  it  has  been  found  to  be  very  good  material 


-»    •£  Outlet  for 


The  Engineer's  Materials 

for  making  roads  and  also  for  concrete,  and  the  mounds 
are  disappearing. 

The  heat  of  a  blast-furnace  is  something  over  2000° 
Fahrenheit,  and  what  with  the  roar  of  the  blast,  the 
rattle  of  the  hoist  which  takes  up  the  ore  and  fuel,  and 
the  noise  of  the  other  machinery  near,  to  stand  by  a 
blast-furnace  is  a  most  awe-inspiring  experience. 

A  blast-furnace  at  night-time  used  to  be  a  glorious 

spectacle, great  flames 
leaping  up  skywards 
as  if  from  an  active 
volcano,  lighting  up 
the  country  for  miles 
round  ;  but  those 
flames  were  really 
good  gases  burning 
to  waste,  and  so  they 
are  not  to  be  seen 
now.  Instead,  the 
mouth  of  the  furnace 
isclosed,andthe  gases 
are  led  away  through 
huge  pipes  to  heat 
boilers  or  drive  gas- 
engines. 

But    the    thought 
will  probably  occur  to 

some  readers,  How,  if  the  furnace  is  closed  at  the  top, 
can  the  ore  and  coal  be  thrown  in  ?  The  explanation 
is  that  the  top  of  the  furnace  is  shaped  like  a  basin  with  a 
hole  in  the  bottom,  and  the  hole  is  stopped  up  with  a 
cone  or  bell-shaped  stopper  as  seen  in  Fig.  14.  The  ore, 
coal,  and  limestone  are  thrown  into  this  basin,  and  when 
the  proper  quantity  has  been  deposited  there  the  plug  is 
lowered  for  a  moment,  and  it  all  falls  into  the  furnace. 
It  takes  several  days  to  get  a  blast-furnace  going, 

90 


-Air 


FIG.  14. — Section  through  centre  of  Blast- 
furnace. 


By  permission  of  Messrs.  IfeUman,  Seaver,  &"  Head,  Lid. 

BLAST  FURNACE  FOR  SMELTING  IRON 

The  striped  structure  near  the  middle  is  the  furnace  itself.  The  inclined  framework 
to  its  left  is  the  hoist  up  which  the  fuel,  ore,  and  limestone  are  carried.  Some  of  the 
large  pipes  are  for  carrying  the  air  blast  to  the  furnace,  and  others  for  taking  away 
the  waste  gases.  The  stack  of  vertical  pipes  in  the  foreground  is  an  arrangement 
for  extracting  the  dust  from  the  waste  gases. 


t<Cc       J    •    ctfc   c^    ec£   tcf     t 


The  Engineer's  Materials 

and  so  it  follows  that  they  work  continuously  day  and 
night,  year  in  and  year  out,  for  long  periods. 

When  the  furnace  is  tapped  the  iron  runs  along  a 
spout,  and  then  falls  on  to  a  bed  of  sand  in  which 
channels  have  been  formed.  It  is  allowed  to  run  until 
these  are  full,  and  then  a  fireclay  plug  is  again  inserted 
in  the  hole  and  the  metal  left  to  cool. 

When  it  has  cooled  it  is  broken  up  into  pieces  of 
about  a  hundredweight  each,  and  is  then  known  as 
"  pig  "  iron,  the  pieces  being  called  "  pigs." 

This  is  by  no  means  pure  iron,  but  contains  from 
3  to  5  per  cent,  of  carbon  besides  other  impurities, 
which  make  it  hard  and  to  a  certain  extent  brittle.  It 
cannot  be  forged  or  welded,  and  it  is  quite  unsuitable 
for  taking  a  severe  tensile  or  pulling  stress,  but  it  is 
able  to  resist  great  pressure,  and  it  has  the  advantage 
that  it  can  be  readily  melted  and  cast  into  a  great 
variety  of  forms.  There  are  a  great  number  of  articles 
made  of  this  "  cast  iron  "  (as  it  is  called,  since  it  is  cast 
in  a  mould),  not  only  in  engineering  works  but  all 
around  us.  The  familiar  black  iron  saucepan,  for 
instance,  which  is  to  be  found  in  every  home,  is  made 
of  cast  iron.  Most  domestic  fire  grates,  garden  rollers, 
the  frame  of  the  typewriter  on  which  these  words  are 
being  written,  and  thousands  of  other  things,  are  made 
in  the  same  way  and  of  the  same  stuff,  while  the  en- 
gineer finds  it  one  of  the  most  useful  of  all  his  materials, 
simply  because  it  can  be  so  easily  cast  into  almost  any 
desired  shape. 

The  making  of  castings  is  not  usually  done  at  the 
same  works  where  the  pig  iron  is  made,  but  the  iron- 
founder  buys  the  pig  iron  from  the  blast-furnace  owner 
and  casts  it  in  his  own  works. 

Here  there  is  a  smaller  edition  of  the  blast-furnace, 
called  a  "  cupola/'  in  which  the  pig  iron  is  melted  up 
ready  to  be  poured  into  the  moulds.  The  moulds  are 

91 


The  Engineer's  Materials 

made  of  sand,  in  iron  boxes,  and  the  making  of  them 
is  a  very  interesting  operation.  Imagine  a  box,  with- 
out bottom  or  lid,  and  divided  horizontally  into  two 
halves,  one  of  which  has  pegs  which  fit  into  holes  in 
the  other,  so  that  the  two  can  always  be  fitted  together 
very  accurately  ;  then  you  will  have  a  good  idea  of  a 
lt  moulding-box."  A  wood  pattern  is  made  the  shape 
of  the  casting  required,  and  is  half  buried  in  sand  in 
the  bottom  half.  The  sand  is,  of  course,  rammed  very 
hard  ;  the  top  surface  is  dusted  over  with  very  dry, 
dusty  sand,  and  then  the  top  half  is  put  on  to  it  and 
filled  with  sand  too.  After  that  has  been  rammed 
hard  the  top  half  is  lifted  off,  the  dry  sand  preventing 
the  sand  in  the  top  half  from  sticking  to  that  in  the 
bottom  half,  so  making  them  part  easily.  Then  the 
pattern  is  taken  out  and  the  top  half  put  on  again. 
A  hole  is  left  in  the  sand  which  forms  the  top  half  of 
the  mould,  and  through  that  the  iron  is  poured,  filling 
the  cavity  left  by  the  pattern  and  so  producing  a 
perfect  replica  of  it  in  iron. 

When  there  are  hollows  in  the  casting,  such  for 
example  as  the  inside  of  a  pipe,  a  core  of  wet  sand  is 
made  and  baked  in  an  oven  until  it  is  hard,  almost  like 
brick,  and  that  is  laid  in  the  mould  so  as  to  form  the 
hollow. 

The  old-fashioned  way  of  ramming  the  sand  was  for 
a  man  to  do  it  with  a  long  iron  rammer,  and  in  many 
cases  that  is  the  only  practicable  way  still,  but  many 
things  can  be  moulded  by  machinery,  and  where  that  is 
feasible  it  is  much  cheaper.  Some  of  these  machines 
are  simply  presses.  The  pattern  is  cut  in  half  and  each 
half  fixed  on  a  board  ;  the  moulding-box  is  put  over  it, 
filled  with  sand,  and  heaped  up.  The  movement  of  a 
handle  then  causes  a  block  to  descend  upon  the  heaped- 
up  sand  and  give  it  one  or  two  vigorous  squeezes, 
thereby  making  it  hard  and  solid.  The  machine  is 

92 


The  Engineer's  Materials 

often  worked  by  compressed  air.  Another  form  of 
moulding  machine,  however,  is  rather  more  interesting, 
since  it  utilises  a  principle  which  we  are  familiar  with 
in  very  different  circumstances.  Probably  every  one 
has  at  some  time  or  other  seen  a  grocer  fi41  a  bag  with 
sugar,  and  has  noticed  that  he  invariably  consolidates 
the  sugar  by  giving  the  bag  one  or  two  smart  bumps 
on  the  counter.  In  the  type  of  moulding  machine 
known  as  "jarrers"  this  idea  is  used.  The  pattern  is 
fixed  on  a  board  as  in  the  other  case,  and  the  board  is 
fixed  on  to  a  table.  Then  the  box  is  put  on  too,  and 
filled  with  sand.  On  the  movement  of  a  small  handle 
the  table  is  raised  an  inch  or  so,  with  the  pattern, 
moulding-box,  and  sand  on  it,  and  then  simply  dropped. 
This  is  repeated  very  rapidly  for  a  few  seconds,  at  the 
end  of  which  time  the  sand  is  hard  and  solid. 

The  methods  I  have  described  apply,  of  course,  only 
to  very  simple  castings.  Some  complicated  ones  need 
to  have  moulding-boxes  made  in  a  large  number  of 
parts  and  the  use  of  a  number  of  cores  of  different 
shapes. 

By  heating  cast  iron  for  a  considerable  time  and 
then  allowing  it  to  cool  very  slowly  it  can  be  made  less 
brittle,  and  then  it  is  called  "  malleable  cast  iron." 
That  can,  however,  only  be  done  with  small  castings, 
and  it  greatly  increases  the  cost,  to  say  nothing  of 
taking  several  weeks  to  do. 

By  reducing  the  amount  of  carbon  in  the  iron  to 
say  \  to  \  per  cent,  it  can  be  made  flexible  and 
elastic  and  capable  of  being  forged  and  welded.  It  is 
then  known  as  "  wrought  iron,"  and  it  is  made  by  a 
process  called  "  puddling."  Pig  iron  is  melted  in  a 
small  furnace,  much  smaller  than  a  blast-furnace,  and 
of  a  different  form  altogether.  It  may  best  be  described 
as  a  large  covered  cauldron  containing  liquid  iron. 
The  "  puddler  "  has  a  long  iron  rake  which  he  inserts 

93 


The  Engineer's  Materials 

through  a  hole  and  stirs  the  iron  about.  As  he  does 
this  he,  of  course,  exposes  it  to  the  air,  and  so  the 
carbon  burns  out  of  it  and  it  becomes  a  thick  pasty 
mass.  This  the  puddler  manipulates  with  his  rake  into 
lumps,  which  he  then  rakes  out  of  the  furnace.  The 
lumps  are  then  heated  again,  but  not  to  melting-point 
this  time,  and  are  placed  in  a  pile  under  a  powerful 
hammer  and  beaten  into  a  block,  which  is  subsequently 
rolled  into  plates,  bars,  sheets,  or  whatever  it  may  be 
required  for. 

This  wrought  iron  is  "  stringy  "  in  its  nature,  so  that 
while  it  can  be  bent  without  fracture  in  one  direction  it 
will  be  liable  to  break  if  bent  the  other  way.  For  this 
reason  and  also  on  account  of  its  inferior  strength,  it  has 
largely  been  superseded  by  steel,  which  has  no  "  grain." 
Wrought  iron  is  still  used,  however,  sometimes,  in 
preference  to  steel,  because  it  rusts  less  quickly.  Steel 
is  intermediate  between  cast  iron  and  wrought  iron,  in- 
asmuch as  it  contains  about  i  to  i^  per  cent  of  carbon. 
Thus  we  see  that  the  differences  in  the  various  kinds  of 
iron  (for  steel  is  simply  a  kind  of  iron)  are  due  mainly 
to  the  differing  proportions  of  carbon  which  they 
contain.  Pure  iron  is  for  practical  purposes  useless. 

Steel  puzzles  people  very  much,  for  knives  are  made 
of  it,  for  instance,  and  fine  edge  tools  and  delicate 
instruments,  yet  rails  and  girders  and  other  rough, 
heavy  things  are  said  to  be  made  of  it  too.  Can  it  be 
that  they  are  all  made  of  the  same  material  ?  The 
answer  is  that  although  they  are  all  steel  the  steels  are 
of  very  different  quality.  For  instance  soft  steel  ("  mild 
steel,"  as  it  is  called)  costs  only  about  .£4  or  .£5 
a  ton,  while  high-class  steel  such  as  tools  are  made  of 
may  cost  as  much  as  ^100  a  ton.  The  difference 
depends  on  the  composition,  mainly  on  the  precise 
amount  of  carbon  which  they  contain.  Then  there  are 
other  kinds  of  steel  used  for  special  purposes,  such 

94 


The  Engineer's  Materials 

as  the  "  nickel-chrome "  steel  used  for  making  guns. 
These  are  all  nearly  the  same,  only  with  slight  varia- 
tions in  their  constituents,  which  often  result  in  vast 
differences  in  the  properties  of  the  metal. 

It  is  indeed  one  of  the  great  beauties  of  steel  that  it 
can,  by  slight  variations  in  its  composition,  be  made  to 
possess  such  a  great  variety  of  qualities  suitable  for 
different  purposes. 

One  way  of  making  mild  steel  is  called  the  Bessemer 
process,  after  Sir  Henry  Bessemer,  who  invented  it. 
The  iron,  as  it  comes  from  the  blast-furnace,  is  placed 
in  a  vessel  called  a  converter,  and  a  blast  of  air  is 
blown  through  it.  The  air  actually  bubbles  up  through 
the  liquid  metal,  so  that  oxygen  (which  is,  of  course,  one 
of  the  constituents  of  the  air)  is  brought  into  contact 
with  every  particle  of  iron,  with  the  result  that  the 
carbon  in  the  iron  combines  with  it,  just  as  the  carbon 
in  coal  combines  with  the  oxygen  in  the  air  and  forms 
a  coal  fire.  The  consequence  is  that,  after  the  air  has 
been  blown  through  the  metal  for  a  while,  the  con- 
verter contains  a  mass  of  practically  pure  iron.  A 
certain  quantity  of  a  special  iron  ore  called  "  spiegel- 
eisen,"  which  contains  a  known  quantity  of  carbon,  is 
then  thrown  in,  and  the  result  is  a  mass  of  steel  con- 
taining just  the  desired  amount  of  carbon. 

The  converter  is  a  curiously  shaped  vessel  with  holes 
in  the  bottom  for  the  air  blast  to  come  up  through. 
It  is  supported  on  two  pivots,  one  on  each  side,  so  that 
it  can  be  tilted  into  a  horizontal  position  for  the  iron 
to  be  poured  in  ;  in  that  position  the  iron  does  not 
reach  the  air-holes.  When  it  has  been  filled,  the  blast 
is  turned  on  and  the  converter  swung  round  into  an 
upright  position,  so  that  the  air  blows  up  through  the 
metal.  When  the  process  is  complete  the  converter  is 
turned  down  again  before  the  blast  is  turned  off.  But 
for  this  arrangement,  of  course,  the  liquid  metal  would 

95 


The  Engineer's  Materials 

run  through  the  holes  in  the  bottom,  and  the  whole 
process  would  be  impossible.  It  is  interesting  to  know 
that  Sir  Henry  Bessemer,  whose  name  is  now  famous 
throughout  the  world  in  connection  with  the  manu- 
facture of  steel,  was  not,  when  he  made  this  invention, 
a  steel  maker.  He  was  an  engineer,  it  is  true,  but  his 
business  was  the  manufacture  of  bronze  powder,  and 
he  only  experimented  in  the  manufacture  of  steel  as 
an  amateur. 

The   other  great   method   of  making    mild   steel   is 
known  as  the  Siemens-Martin  process,  again  after  its 


FIG.  15. — Bessemer  Converter,  a,  Vertical  position  ;  see 
how  the  air  is  blowing  up  through  the  steel,  b,  Hori- 
zontal position  for  charging  and  emptying,  c,  Front 
view,  showing  how  the  converter  swings  on  pivots. 

inventors.  The  furnace  in  which  this  is  carried  out 
might  be  described  as  a  shallow  oblong  bath,  the  heat 
being  supplied  by  gas  similar  to  the  producer  gas  de- 
scribed in  a  previous  chapter  in  connection  with  gas- 
engines. 

At  each  end  of  the  furnace  there  are  two  huge  brick 
flues,  through  one  of  which  comes  the  gas  and  through 
the  other  air.  On  entering  the  furnace  the  gas  and  air 
mingle  and  burst  into  flame,  the  roof  of  the  furnace 
being  so  made  as  to  deflect  the  flames  down  on  to  the 
surface  of  the  iron,  while  the  waste  gases  which  are 
produced  by  the  combustion  (the  smoke,  as  it  were, 
only  there  is  little  or  none  of  that  dirt  which  we 
associate  with  smoke)  escape  through  the  two  flues  at 


The  Engineer's  Materials 

the  opposite  end.  Now  that  brings  us  to  a  very  in- 
teresting thing.  Those  waste  gases  are  very  hot,  and 
it  would  be  a  great  pity  to  lose  all  their  heat ;  yet  how 
can  it  be  recovered  ?  The  means  adopted  are  ridicu- 
lously simple. 

The  two  flues  at  each  end  are  each  connected  with 
two  large  chambers,  filled  with  loosely  stacked  bricks, 
so  that  the  hot  gases,  as  they  pass  out,  have  to  go 
around  and  between  these  bricks,  and  in  so  doing 
impart  to  them  intense  heat.  After  that  has  been 
going  on  for  a  while  the  course  of  the  gases  is  re- 
versed, and  the  gas  and  air  come  in  at  the  opposite  end, 


FIG.  16. — Diagram  showing  how  the  waste  gases  in  a  Regenerative 
Furnace  are  made  to  give  up  some  of  their  heat,  which  later  is 
carried  back  into  the  furnace. 

while  the  waste  gases  go  out  where,  a  moment  before, 
the  new  gas  and  air  were  coming  in.  Thus  the  fresh 
gas  and  air,  passing  through  the  heated  bricks,  pick  up 
and  carry  back  into  the  furnace  a  great  deal  of  the 
heat  which  was  taken  out  a  short  time  before  by  the 
waste  gas.  So  the  process  goes  on,  first  one  way  and 
then  the  other ;  the  stacks  of  bricks  are  first  heated  by 
the  waste  gas,  and  then  in  turn  they  heat  the  gas  and 
air  coming  into  the  furnace.  Furnaces  so  arranged 
are  called  "  regenerative  "  furnaces. 

Thus  the  iron  is  boiled,  as  it  were,  until  much  of 
the  carbon  has  been  burnt  out  of  it,  and  by  the  addition 
of  certain  special  ores  the  right  mixture  has  been  ob- 
tained. 

The  men  who  attend  the  furnaces  have  to  wear  dark- 

97  G 


The  Engineer's  Materials 

blue  spectacles,  as  the  glare  of  the  boiling  metal  is  so 
great  that  with  the  naked  eye  absolutely  nothing  can 
be  seen.  Viewed  through  dark  glasses,  however,  it  is 
a  magnificent  sight — a  lake  of  fire,  bubbling  and  surging, 
and  when  the  lumps  of  ore  are  thrown  in,  the  splashes 
which  arise  are  more  glorious  than  the  finest  display 
of  fireworks. 

When  the  steel  is  ready,  it  is  run  out  of  the  furnaces 
into  ladles  and  cast,  in  iron  moulds,  into  ingots — great 
rectangular  blocks  weighing,  perhaps,  as  much  as  i  o  tons 
each. 

The  next  stage  is  the  rolling  of  these  ingots  into 
rails,  girders,  plates,  bars,  or  whatever  form  may  be 
required.  This  is  done  in  a  rolling  mill.  It  is  in 
principle  just  like  the  ordinary  domestic  mangle.  The 
ingot,  having  been  reheated  to  a  white  heat  in  an 
underground  furnace  known  as  a  "  soaking  pit "  (since 
the  ingot  must  be  thoroughly  soaked  through  with  heat), 
is  lifted  by  a  huge  pair  of  pincers  attached  to  a  power- 
ful crane  and  laid  on  the  "  live  rollers."  These  are  a 
large  number  of  rollers  laid  near  together  and  parallel 
to  each  other,  just  above  the  level  of  the  floor,  all 
rotating  in  the  same  direction  and  at  the  same  speed. 
As  soon  as  the  ingot  rests  on  these  they  carry  it  forward 
to  the  rolling  mill,  where  it  passes  between  the  rollers. 
These  are  different  from  the  rollers  of  the  mangle,  to 
which  I  compared  them  just  now,  in  that  they  have 
grooves  in  them  shaped  according  to  the  work  that  is 
required  of  them.  The  first  pair  of  rollers  have  large 
grooves,  so  that  they  can  take  in  a  whole  ingot  and 
reduce  its  girth  a  little,  while  increasing  its  length. 
Then  it  passes  on  over  other  live  rollers,  until  it  reaches 
another  rolling  mill,  through  which  it  passes  again  and 
again,  backwards  and  forwards,  each  time  getting  smaller 
and  smaller  in  section,  until  at  last  it  is  a  rail  or  girder 
or  angle  iron,  or  whatever  it  is  intended  to  become. 


The  Engineer's  Materials 

Plates  are  made,  too,  in  just  the  same  way,  the  only 
difference  being  in  the  shape  of  the  rollers.  / 

Specially  designed  steam-engines  have  to  be  employed 
to  drive  these  rolling  mills,  owing  to  the  exceptional 
circumstances  under  which  they  work.  Consider  it 
for  a  moment.  Merely  to  spin  the  rolls  round  requires 
scarcely  any  power  at  all,  but  the  moment  they  grip 
the  end  of  the  approaching  ingot  enormous  force — 
many  thousands  of  horse-power — is  required  to  be 
exerted  all  at  once.  In  some  modern  mills,  electric 
motors  are  used  for  this  purpose,  each  of  which  is 
provided  with  an  enormous  fly-wheel,  which  the  motor, 
when  it  is  working  light,  drives  up  to  a  great  speed. 
Then  as  soon  as  the  entrance  of  the  ingot  into  the 
rolls  causes  the  motor  to  slow  down  somewhat,  the 
great  force  stored  up  in  the  momentum  of  the  fly-wheel 
comes  into  play  and  assists  the  motor.  Thus,  when 
working  light,  the  motor  is  able  to  store  up  a  supply 
of  energy  which  comes  to  its  assistance  when  it  is 
hard  pressed.1 

Electricity,  in  fact,  plays  a  great  part  in  modern 
steelworks. 

The  furnaces  are  often  fed  with  material  by  a  huge 
electrically-driven  "  charging  machine."  This  travels 
on  rails,  either  overhead  or  else  on  the  ground,  and 
possesses  a  marvellous  mechanical  arm,  the  action  of 
which  is  remarkably  like  that  of  the  human  arm.  The 
machine  can  move  up  and  down  in  front  of  a  long 
row  of  furnaces,  and  if  one  of  them  needs  some  more 
iron  putting  in,  it  will  run  perhaps  to  the  other  end  of 
the  shed,  pick  up  a  box  containing  several  tons  of 
material,  bring  it  back,  and  put  it  through  the  door  of 
the  particular  furnace  that  needs  it.  Then,  having 
turned  the  box  over  to  tip  out  its  contents,  it  will 
withdraw  it  and  take  the  empty  box  back.  All  the 

1  Page  80  shows  this  principle  applied  to  hauling  coals  up  out  of  a  coal  pit. 

99 


The  Engineer's  Materials 

different  motions  are  worked  by  electric  motors,  and 
the  whole  thing  is  controlled  by  one  man,  who  stands 
on  a  little  platform  on  the  machine  itself. 

Then,  in  some  works,  there  are  machines  of  a  similar 
description  which,  instead  of  a  hand  for  taking  hold 
of  the  boxes  of  material,  are  armed  with  claws  by 
which  they  can  pick  up  a  hot  ingot  and  hand  it  about 
as  easily  as  a  hostess  can  hand  a  cup  of  tea  to  a  guest 
(see  page  98).1 

The  steel  of  which  tools  are  made  is  produced  by 
quite  a  different  process.  Instead  of  being  made  from 
the  crude  iron  as  it  comes  from  the  blast-furnace,  the 
finest  and  purest  wrought  iron  is  melted  up  with  other 
ingredients  in  a  crucible.  In  the  case  of  mild  steel, 
it  is  a  refining  process :  the  impure  iron  is  put  in  the 
furnace  and  the  impurities  are  got  rid  of  until  the 
desired  mixture  is  left,  while  in  the  other  it  is  simply 
mixing,  the  purest  of  materials  being  melted  up  to- 
gether. Moreover,  while  mild  steel  is  turned  out  by  the 
hundred  tons,  crucible  steel  is  made  in  lots  of  a  few 
hundredweight.  Thus  the  expensive  materials  and 
small  quantity,  together,  account  for  the  large  difference 
in  cost. 

Both  mild  steel  and  crucible  steel  can  be  cast  in 
moulds  just  as  cast  iron  is,  and  there  has  been  a  great 
development  in  the  use  of  mild  steel  castings  in  recent 
years,  as  they  are  stronger  and  less  brittle  than  iron 
castings,  and  also  (an  important  point  for  electrical 
machinery)  they  possess  better  magnetic  qualities  as 
well. 

But,  of  course,  the  many  varieties  of  iron  and  steel 
do  not  exhaust  the  list  of  materials  used  by  the  engineer. 
Some  of  the  more  important  of  the  others  will  be 
described  in  the  next  chapter. 

1  The  methods  by  which  electricity  is  used  to  melt  iron  and  steel  are  referred 
to  in  Chapter  XXII. 

100 


CHAPTER   VII 

MORE   MATERIALS 

BESIDES  iron  and  steel  there  are  two  other  materials 
largely  used  by  the  engineer  of  to-day.  These  are 
Portland  cement  and  copper. 

The  former,  as  we  shall  see  later,  has  of  recent 
years  entered  into  a  remarkable  partnership  with  steel, 
giving  us  the  wonderful  new  building  material,  "  ferro- 
concrete," while  in  railway  construction,  harbour  works, 
and  all  great  public  undertakings  it  is  invaluable. 

Despite  its  name,  it  has  nothing  to  do  with  the 
place  called  Portland,  except  that  the  place  has  given 
its  name  to  a  kind  of  building  stone  which  is  found 
there,  and  Portland  cement,  if  mixed  with  water  and 
allowed  to  set,  looks  like  this  Portland  stone. 

It  is  a  mixture  of  chalk  and  clay,  or  as  the  chemist 
would  say,  silica,  which  is  derived  from  the  chalk  and 
alumina,  the  material  of  which  clay  is  made.  The 
chalk  is  obtained  from  a  quarry,  and  the  clay  either 
from  beds  or  pits  or  from  the  mud  of  certain  rivers. 

There  are  two  processes  by  which  it  is  manufactured, 
known  as  the  "wet"  and  the  "dry"  respectively.  In 
the  older,  the  "  wet,"  the  clay  is  used  in  a  wet  state, 
as  it  comes  from  the  river  bed  whence  it  has  been 
dredged  up.  It  generally  comes  to  the  works  in  barges, 
and  it  is  sent  first  to  the  "  wash  mill,"  a  machine  in 
which  it  and  chalk  from  a  quarry  near  by,  in  the 
proportions  of  about  one  to  three,  are  thoroughly 
mixed  up  and  stirred  together,  with  water.  This  is  a 

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More  Materials 

1  Very  'important  part  of  the  process,  as  the  quality  of  the 
cement  depends  upon  the  two  materials  being  very 
intimately  mixed  together. 

The  wash  mill  having  stirred  it  up  very  thoroughly, 
until  it  looks  very  like  milk,  the  (t  slurry,"  as  it  is  now 
called,  passes  to  a  rotary  kiln,  a  very  interesting  piece 
of  machinery.  It  is  a  large  iron  tube  formed  of  plates 
riveted  together  as  we  see  the  plates  riveted  together 
in  a  boiler.  It  may  be  as  long  as  50  yards  and 
7  or  8  feet  in  diameter,  and  at  intervals  along  it  there 
are  strong  iron  rings  entirely  encircling  it,  which  are 
supported  on  rollers  so  "that  the  whole  structure  can 
turn  round  and  round  bodily.  It  is  of  great  weight, 
for  besides  the  steel  shell  there  is  a  lining  of  firebrick, 
and  inside  that  the  material  that  is  being  treated.  It  is 
an  impressive  sight,  therefore,  to  see  this  great  heavy 
drum  slowly  turning  over  and  over,  and  of  course  it 
needs  a  powerful  engine  to  drive  it. 

One  end  is  slightly  higher  than  the  other,  and  at  the 
upper  end  the  slurry  is  fed  in  through  spouts.  At  the 
other  end  there  is  blown  in  a  jet  of  air  and  coal  dust. 
Now  coal  dust,  as  was  noticed  in  an  earlier  chapter,  if 
fine  and  mixed  with  air,  will  burn  like  gas,  and  so  as  the 
slurry  trickles  down  from  the  upper  end  it  meets  the 
hot  gases  and  eventually  the  hot  flames  of  a  very  efficient 
coal  fire  coming  from  the  other  end.  It  is  thus  first  of 
all  dried,  and  all  the  water  driven  out  of  it  (it  would,  of 
course,  stick  to  the  bottom  of  the  furnace  in  a  lump 
but  for  the  continual  movement),  then  as  it  travels 
along,  getting  nearer  and  nearer  to  the  hottest  part  of 
the  furnace,  it  is  well  burnt,  and  falls  out  at  the  lower 
end  in  the  form  known  as  "  clinker."  The  milky-looking 
liquid  has  by  that  time  been  turned  into  a  hard,  stony 
solid. 

Of  course  the  clinker  as  it  falls  from  the  "  rotary  " 
is  very  hot,  and  according  to  modern  practice  that  heat 

102 


More  Materials 

must  not  be  lost  if  it  can  possibly  be  captured  and 
turned  to  some  further  use.  Under  the  kiln,  therefore, 
there  is  another  tube,  a  sort  of  miniature  of  the  larger 
tube  above,  and  into  this  the  hot  clinker  falls.  The 
lower  tube  or  "  cooler/'  as  it  is  called,  slopes  the  opposite 
way  to  the  kiln,  and  so  the  clinker  starts  to  travel  back 
to  the  place  whence  it  started,  meeting  a  draught  of 
cold  air  as  it  goes.  This  air  cools  it  quickly,  but,  what 
is  more  important,  it  heats  the  air,  and  it  is  the  same 
air  which  is  injected  with  the  coal  dust  into  the  kiln  ; 
so,  becoming  heated  in  this  way,  the  air  carries  back 
into  the  furnace  a  great  deal  of  the  heat  which  the 
clinker  has  brought  out  with  it. 

This  form  of  kiln  is  a  remarkable  contrast  to  those 
which  used  to  be  in  vogue.  With  them  the  slurry  was, 
after  mixing,  allowed  to  dry  in  tanks  until  it  was  about 
the  consistency  of  butter.  It  was  then  dug  out  in  lumps 
and  stacked  in  a  brick  chamber  along  with  alternate 
layers  of  coke.  The  whole  mass  was  then  ignited,  and 
when  the  coke  had  all  burnt  the  kiln  was  opened  and 
the  clinker  taken  out.  This  meant  alternate  firing  and 
cooling,  not  a  continuous  process  like  the  rotary,  and  a 
great  deal  of  heat  was  lost. 

After  leaving  the  rotary  kiln  the  clinker  passes  to  the 
grinding  mills. 

That  is  the  wet  process.  In  the  dry,  the  clay  is 
obtained  in  as  dry  a  state  as  possible,  and  after  being 
subjected  to  a  little  heat  to  make  it  quite  dry  it  is  ground 
up  with  the  right  quantity  of  chalk,  often  in  what  is 
called  a  ball  mill — that  is,  a  revolving  drum  with  heavy 
steel  balls  in  it,  which  roll  and  tumble  about  as  the  mill 
is  rotated,  and  so  pound  up  the  material  with  which  it 
is  partly  filled.  This  powder  is  then  mixed  with  a  little 
slurry,  and  formed  into  bricks  about  the  same  size  as 
the  ordinary  building  bricks.  These  are  fired  in  a 
vertical  kiln,  a  tall  tower  heated  by  gas  at  the  bottom, 

103 


More  Materials 

the  bricks  being  fed  in  at  the  top  and  withdrawn  a  few 
at  a  time  at  the  bottom,  so  that  here  again  the  process 
is  continuous. 

The  final  grinding  of  the  clinker  into  the  fine,  impal- 
pable powder  which  is  the  finished  cement  is  a  very 
important  matter.  The  reason  why  cement  after  being 
wetted  turns  into  a  hard,  solid  mass  is  because  of  the 
process  of  crystallisation  which  is  set  up  among  the 
particles  when  they  come  into  contact  with  water. 
They  crystallise  into  such  a  shape  that  the  whole  mass 
of  crystals  interlock  with  one  another,  and  it  is  that 
interlocking  which  holds  them  together  and  makes  a 
myriad  particles  into  a  solid  block.  We  see,  then,  that 
the  strength  is  due  to  the  mixture  of  the  cement  and 
water,  and  it  is  quite  clear  that  the  finer  the  particles 
into  which  the  cement  is  divided  the  more  thorough 
will  the  mixture  be  and  the  stronger  the  resulting  block. 
It  used  to  be  ground  with  millstones  just  as  flour  was 
ground  in  the  old  windmills,  but  now  machines  called 
"  tube-mills "  are  generally  used  for  the  purpose. 
These  grind  it  much  finer  than  the  old  stones. 

The  difference  between  ball-mills  and  tube-mills  it 
may  be  interesting  to  explain.  The  former  is  a  large 
drum,  perhaps  10  feet  long  and  6  feet  diameter,  partially 
filled  with  steel  balls,  revolving  about  thirty  times  a 
minute.  The  latter  is  also  a  drum,  and  is  also  partially 
filled  with  steel  balls,  but  it  is  longer  and  narrower,  say 
24  feet  long  and  4  feet  diameter,  and  it  rotates  about 
half  as  fast  again.  Thus  the  material,  passing  from  end 
to  end,  is  longer  subject  to  the  pounding  of  the  balls, 
and  the  latter,  because  of  the  higher  speed,  are  more 
energetic  in  their  action,  resulting  in  a  very  fine  powder 
being  produced. 

Cement  is  now  being  made,  too,  from  the  slag  which 
comes  from  the  blast-furnaces  in  ironworks. 

The  molten  slag  runs  on  to  rapidly  revolving  rollers, 

104 


More  Materials 

and  at  the  same  time  water  is  sprayed  on  to  it.  Thus 
it  is  cooled  and  solidifies  in  granulated  form.  It  is  then 
left  for  some  days  to  cool  thoroughly. 

After  that  it  is  broken  up  into  small  pieces  and  ground 
in  a  "  ball-mill/'  the  grinding  being  completed  in  a 
« tube-mill." 

We  come  now  to  our  third  great  material,  copper. 

At  one  time  the  chief  use  of  this  metal  was  to  cover 
the  bottoms  of  ships,  but,  with  the  advent  of  the  iron 
ship,  that  use  died  out.  About  the  same  time,  however, 
there  arose  a  fresh  demand  for  copper  for  electrical 
purposes,  and  that  demand  is  so  great  that  although  the 
production  has  increased  very  greatly  it  is  barely  able 
to  supply  the  requirements  of  the  great  electrical 
industry. 

Copper,  like  iron,  is  found  in  the  form  of  ore,  in 
combination  with  other  substances,  including,  however, 
unlike  iron,  some  impurities  which  are  more  valuable 
than  itself.  The  refiner  of  iron  gets  nothing  more 
valuable  than  blast-furnace  slag,  which  was  for  years  an 
absolute  drug  in  the  market  (people  would  not  even 
take  it  away  unless  they  were  paid  to  do  so),  but  the 
refiner  of  copper  gets  gold  and  silver. 

The  first  thing  that  is  done  to  the  ore  is  to  heat  it  to 
a  moderate  temperature — "  calcine  "  it,  is  the  technical 
term.  That  is  to  drive  off  the  sulphur.  The  ore  is  in 
the  calcining  furnace  for  from  twenty-four  to  thirty-six 
hours,  during  which  time  it  has  to  be  stirred  about  or 
agitated  in  some  way  so  that  the  process  may  go  on 
uniformly  throughout  the  whole  mass  of  ore. 

Then  it  goes  to  a  furnace  to  be  smelted.  This  is 
very  like  what  is  done  with  iron,  which,  as  we  have  seen, 
is  first  roasted  at  a  comparatively  low  temperature  and 
then  taken  to  the  blast-furnace  ;  and  the  similarity  does 
not  end  there,  for  the  furnaces  used  for  smelting  copper 
are  most  of  them  either  like  the  blast-furnace  that  is 

105 


More  Materials 

used  for  iron,  or  else  like  the  Siemens  steel  furnace.  The 
product  from  these  furnaces  is,  however,  not  a  nearly 
pure  metal  like  pig  iron  but  a  substance  called  "matte," 
which  only  contains  from  45  to  50  per  cent,  of  copper, 
so  that  another  process  has  to  be  gone  through. 

Again  we  find  a  remarkable  similarity  with  the  manu- 
facture of  iron,  for  the  plant  which  is  used  very  largely 
for  this  is  the  Bessemer  Converter.  The  strangeness 
of  the  situation  increases,  too,  when  we  find  that  while 
the  steelmaker  uses  the  Bessemer  Converter  to  burn 
carbon  out  of  iron,  the  copper  smelter  uses  it  to  burn 
iron  out  of  copper.  A  converter  is  of  course  always 
lined  with  a  kind  of  mortar,  made  of  sand,  in  order  to 
protect  the  iron  shell  from  destruction  by  the  heat.  In 
the  steelworks  this  lining,  however,  plays  a  further  part 
in  the  process,  for  certain  ingredients  are  mixed  with  it 
which  enter  into  the  chemical  changes  by  which  the 
steel  is  formed,  and  the  same  is  the  case  at  the  copper- 
works.  There  the  silica  in  the  lining  having  an  affi- 
nity for  iron,  the  two  combine  and  form  slag,  leaving 
the  copper  with  only  about  i  per  cent,  of  impurities. 

This  i  per  cent.,  however,  is  partly  gold  and  silver, 
which  are  worth  some  expense  to  recover,  while  the  re- 
mainder of  the  i  per  cent,  consists  of  other  metals — 
such  as  arsenic,  antimony,  bismuth,  tellurium,  and  silu- 
rium,  which  spoil  the  copper  as  a  conductor  of  elec- 
tricity. While,  therefore,  the  gold  and  silver  are  worth 
recovering  for  their  own  sake,  the  others  are  worth 
extracting  for  the  sake  of  the  copper,  and  the  method 
most  largely  adopted  is  electrical.  It  is  indeed  very 
curious  that  whereas  the  dynamo  is  the  cause  of  the 
large  demand  for  this  very  pure  copper,  it  is  also  the 
dynamo  which  enables  it  to  be  produced,  for  only  by 
its  means  can  those  large  currents  be  generated  which 
are  necessary  for  the  process. 

The  process  is  precisely  similar  to  that  by  which  our 

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More  Materials 

spoons  and  forks  (or  rather  the  spoons  and  forks  of 
some  of  us)  are  electro-plated.  The  scientific  name 
for  the  process  is  lt  electrolysis,"  and  briefly  it  is  this. 

If  a  piece  of  metal  be  suspended  in  a  suitable  liquid 
and  connected  to  the  positive  pole  of  a  battery  or 
dynamo  (the  end,  that  is,  from  which  the  current  ap- 
pears to  flow),  and  some  other  object — it  matters  not 
what,  so  long  as  it  is  a  conductor  of  electricity — be  hung 
in  the  same  liquid  and  connected  to  the  negative  pole 
of  the  battery  or  dynamo  and  the  current  then  turned 
on,  very  minute  particles  of  the  metal  plate  will  be  dis- 
solved off,  will  pass  through  the  liquid,  and  become  de- 
posited on  the  second  object  whatever  it  may  be.  In 
electro-plating  the  current  thus  conveys  particles  from  a 
plate  of  silver  and  deposits  them  upon  the  object  of  a 
baser  metal  which  it  is  desired  to  cover,  and  so  a  fine 
layer  of  silver  is  spread  over  the  object. 

The  plate  of  metal  to  which  the  current  passes  from 
the  dynamo  is  called  the  "  anode,"  and  the  other  the 
"  cathode." 

In  making  "  electrolytic "  copper  the  anodes  are 
slabs  of  the  99  per  cent,  pure  copper  referred  to  just 
now,  and  the  cathodes  are  plates  of  copper.  The  cur- 
rent causes  the  anode  to  be  dissolved  and  the  particles 
to  be  deposited  on  the  cathode  ;  and  fortunately  it  can 
be  arranged  so  that  it  is  only  the  particles  of  copper 
which  are  thus  deposited,  while  all  the  other  matters 
settle  to  the  bottom  of  the  tank  in  the  form  of  "  slime." 
The  pure  copper,  when  a  good  quantity  of  it  has  been 
deposited,  is  torn  off  the  cathode,  while  the  slime  is 
drawn  off  at  intervals  and  the  precious  metals  extracted 
from  it. 


107 


CHAPTER  VIII 

THE   ENGINEER'S   TOOLS 

Now  that  we  have  seen  the  materials  which  the 
engineer  uses,  it  will  be  interesting  to  look  at  some  of 
the  tools  with  which  he  fashions  them. 

The  ordinary  man  uses  the  word  tl  tool "  to  indicate 
such  things  as  hammers,  files,  chisels,  and  planes,  but 
those  the  engineer  distinguishes  by  the  name  of  "  hand  " 
tools,  using  the  latter  word  in  a  much  wider  sense 
to  cover  many  very  elaborate  and  wonderful  machines, 
which  he  calls  "  machine  "  tools. 

The  most  useful  of  all  is  the  lathe,  a  machine  in 
which  a  piece  of  metal  can  be  turned  round  while  a 
suitable  cutting-tool  is  held  against  it  so  as  to  take  a 
shaving  off  it  as  it  turns.  Whoever  it  was  that  thought 
first  of  the  idea  of  shaping  things  by  turning  them 
round  in  this  way  must  have  been  a  genius,  and  he 
certainly  conferred  a  great  boon  upon  his  fellow- 
creatures  ;  for  by  this  simple  means  operations  are  made 
quite  easy  which,  without  it,  would  be  difficult  and 
in  some  cases  impossible.  Give  an  expert  workman 
even  a  very  simple  lathe,  and  it  will  be  difficult  to  find 
a  job  which  he  cannot  do  with  it. 

Of  recent  years,  however,  the  lathe  has  undergone 
great  developments.  These  have  been  mainly  in  the 
direction  of  making  it  work  automatically,  so  as  to 
need  the  minimum  of  supervision.  Automatic  lathes 
are  made  which  can  take  in  a  bar  of  metal  and  turn 
it  into  pins  of  any  desired  shape,  cutting  each  off  when 

108 


The  Engineer's  Tools 

done  and  throwing  it  out,  immediately  starting  on  a 
fresh  one  and  so  working  on  continuously. 

Another  important  tool  is  the  planing-machine, 
which  takes  shavings  off  iron  or  steel  as  easily  as  a 
carpenter  planes  soft  wood.  It  consists  of  a  heavy 
iron  table,  which  travels  to  and  fro  with  the  piece  to 
be  planed  bolted  down  upon  it.  Across  it  is  a  sort 
of  bridge  to  which  the  tool  is  fixed,  and  after  each 
journey  of  the  table  this  tool  is  moved  automatically  a 
short  distance.  Thus,  starting  at  one  edge,  it  makes  a 
series  of  parallel  cuts,  gradually  working  its  way  across 
until  the  whole  surface  of  many  square  feet,  it  may  be, 
has  been  planed  quite  level. 

Most  of  us  have  seen  large  circular  saws  at  work 
cutting  wood,  but  the  fact  that  such  saws  can  be  used 
to  cut  iron  and  steel  may  come  as  a  surprise.  Suppose 
we  have  a  steel  girder,  such  as  are  used  for  making  the 
framework  of  large  buildings,  and  we  wish  to.cut  a  foot 
off  its  length,  our  best  way  to  do  it  will  be  with  a 
circular  saw.  The  saw  used  for  iron  is  very  similar 
to  that  used  for  wood,  only  it  is  generally  smaller  and 
it  works  at  a  much  slower  speed.  That  is  because  of 
the  heat.  A  saw  which  has  cut  through  a  piece  even 
of  a  soft  substance  like  wood,  is  quite  hot  when  it  has 
done  its  work,  and  when  it  is  used  for  biting  through 
hard  iron  or  steel  it  naturally  gets  much  hotter  still, 
so  that,  if  it  worked  as  fast  as  a  timber  saw  does,  it 
would  quickly  get  so  hot  as  to  become  softened  and 
useless.  Even  at  its  slow  speed  it  has  to  be  cooled 
and  lubricated  with  a  continual  stream  of  soapy  water. 

There  is  one  very  remarkable  form  of  saw,  called 
a  "  high-speed "  saw,  in  which  this  heating  effect  is 
turned  to  useful  account.  One  very  extraordinary 
feature  about  this  machine  is  that  the  part  which  cuts 
is  often  softer  than  the  thing  which  is  cut,  and  yet 
after  long  use  it  shows  scarcely  any  signs  of  wear. 

109 


The  Engineer's  Tools 

The  revolving  disc  is  not  of  hard  but  of  soft  steel,  and 
instead  of  having  sharp  teeth  it  is  simply  roughened  on 
its  edge.  Yet  it  revolves  very  fast,  so  fast,  indeed,  that 
its  circumference  travels  as  quickly  as  the  fastest  ex- 
press train.  It  is  this  high  speed  which  does  the  cutting 
and  nothing  else,  for  as  soon  as  the  edge  of  the  disc 
touches  the  girder,  or  whatever  has  to  be  cut,  enormous 
heat  is  produced  by  the  friction  ;  so  the  girder  be- 
comes softened  and  the  disc  easily  rubs  its  way  through. 
So  easy  is  this  rubbing  action  that,  as  I  mentioned  just 
now,  the  disc  itself  shows  scarcely  any  wear.  But 
how  is  it,  it  will  probably  be  asked,  that  the  disc  is 
not  softened  too  ?  It  is  because  in  the  case  of  the 
girder  the  friction  takes  place  all  at  one  spot,  and  so  it 
is  softened  there,  while,  in  the  case  of  the  disc,  a  part 
which  is  at  one  moment  in  contact  with  the  girder  is 
the  next  moment  flying  through  the  air  and  so  losing  its 
heat,  and  before  the  revolution  of  the  disc  has  brought 
that  particular  part  back  to  the  girder  again  it  will  be 
quite  cold,  so  that  the  heat  in  the  disc  itself  is  dissipated 
as  quickly  as  it  is  developed.  These  machines  cut  with 
surprising  speed,  for  a  girder  12  inches  deep  can  be 
cut  right  through  in  less  than  a  minute. 

But  of  tools  used  for  cutting,  perhaps  the  most 
remarkable  of  all  is  the  oxygen  blow-pipe.  This  is 
a  little  tool  something  the  shape  of  a  pistol,  which  a 
workman  can  easily  hold  in  one  hand.  It  is  connected 
by  a  flexible  tube  to  a  cylinder  of  compressed  oxygen, 
and  by  another  tube  to  a  supply  of  coal-gas.  Thus 
a  jet  of  oxygen  and  a  jet  of  coal-gas  issue  from  the 
nozzle  at  the  end  of  the  blow-pipe,  and,  mingling  there, 
produce  a  fine  point  of  flame  burning  with  intense 
heat.  If  this  be  directed  upon  the  edge  of  a  thick 
bar  or  plate  of  "steel  it  will  in  a  few  seconds  melt 
a  tiny  groove  in  it,  and,  if  the  pipe  be  moved  along, 
that  groove  can  be  developed  into  a  cut  and  in  that 

I  10 


The  Engineer's  Tools 

way  very  thick  pieces  of  steel  can  be  severed  quite 
easily.  The  harder  the  steel,  too,  the  more  easily 
is  it  cut,  for  hard  steel  contains  more  carbon  than 
soft,  and  that  has  a  tendency  to  burn  with  oxygen, 
actually  increasing  the  heat  of  the  flame.  A  bar 
of  iron  a  foot  long  can  be  cut  right  down  the  centre 
in  fifty  seconds.  It  is  said  that  scientific  burglars 
have  been  known  to  use  these  blow-pipes  to  open 
safes  with ;  but  a  very  strange  thing  about  them  is 
that,  while  they  will  cut  hard  steel  of  any  thickness 
almost  like  butter,  they  are  completely  baffled  by  a 
thin  sheet  of  copper.  The  reason  of  this  is  that 
copper  is  such  a  good  conductor  of  heat  that  the 
heat  of  the  flame  is  conducted  quickly  away,  and 
so  the  part  in  contact  with  the  flame  never  becomes 
hot  enough  to  melt. 

There  is  another  purpose  for  which  the  oxygen 
blow-pipe  is  used,  and  strangely  enough,  it  is  the  exact 
opposite  of  what  I  have  just  been  describing — namely, 
for  joining  pieces  of  metal  together.  Wrought  iron, 
and  also  some  qualities  of  steel,  can  be  heated  until 
they  reach  a  soft  plastic  state,  and  if  two  pieces  in 
that  state  are  placed  together  and  hammered,  they 
become  united.  That  process  is  called  "  welding." 
Now  there  are  many  instances  in  which  it  is  im- 
practicable to  do  this  owing  to  the  shape  of  the 
pieces,  and  in  such  cases  they  can  often  be  welded  by 
a  jet  of  oxygen  and  acetylene,  in  a  suitable  blow-pipe. 

The  process,  to  watch,  is  very  like  the  soldering  of 
two  pieces  of  tin  by  a  tinsmith.  The  workman  holds 
the  blow-pipe  in  his  hand  much  as  the  tinman  holds 
his  "iron,"  and  with  it  he  heats  the  two  edges  to 
be  joined  until  they  are  almost  melting.  Then  he 
places  the  end  of  a  piece  of  iron  wire  in  the  flame, 
and,  just  as  if  it  were  solder,  melts  it  into  the  joint. 
Thus  he  works  along  until  the  whole  joint  is  finished, 

ii  i 


The  Engineer's  Tools 

when  a  very  sound  and  strong  job  is  the  result.  Other 
metals  besides  iron  and  steel  can  be  joined  in  this  way. 

It  may  be  interesting  in  this  connection  just  to 
turn  aside  for  a  moment  and  see  how  the  oxygen 
is  made  for  use  in  these  tools.  As  is  well  known,  it 
is  one  of  the  constituent  parts  of  the  air,  forming  in 
fact  about  20  per  cent,  of  the  bulk  of  the  atmosphere, 
the  remaining  80  per  cent,  being  mainly  nitrogen. 

Now  just  as  steam  has  a  liquid  form  for  which  we 
have  a  separate  name,  water,  so  air  has  a  liquid  form, 
only  since  it  has  no  name  of  its  own  we  are  forced  to 
call  it  "  liquid  air."  It  is  not  easy  to  induce  air,  under 
the  conditions  which  exist  around  us,  to  enter  into  the 
liquid  state,  but  great  pressure  and  cold  will  do  it.  Air 
is  therefore  compressed  by  an  air-compressor,  or  pump, 
and  is  forced  to  pass  through  a  coil  of  pipe.  At  the 
bottom  of  this  coil  it  escapes  and  passes  upwards  around 
the  outside  of  the  pipe. 

When  a  gas  is  compressed  it  always  becomes  hotter. 
The  force  expended  in  compressing  it  is  converted  into 
heat,  and  as  soon  as  it  is  allowed  to  expand  again  it 
loses  exactly  the  same  amount  of  heat  that  it  gained 
when  it  was  compressed.  If,  therefore,  you  take  any 
heat  out  of  it  while  it  is  under  pressure  it  will  be  that 
much  colder  when  it  is  expanded  than  it  was  before  it 
was  compressed.  That  is  to  say,  if  you  compressed  air 
at  50  degrees  until  it  had  reached  100  degrees,  and  then 
cooled  it  by  30  degrees  down  to  70,  when  you  expanded 
it  again  it  would  be  only  20  degrees — the  original  50, 
that  is,  less  the  30  which  you  extracted. 

So,  when  you  compress  the  air  in  the  liquid-air 
machine  it  gains  heat,  some  of  which  it  loses  on  its  way 
through  the  coil,  and  when  it  escapes  at  the  bottom  it 
is  therefore  somewhat  cooler  than  it  was  to  start  with. 
That  in  turn  passing  upward  cools  the  coil  still  more, 
so  that  the  next  lot  of  air  which  escapes  is  colder  still ;  and 

I  12 


The  Engineer's  Tools 

so  the  process  goes  on,  the  air  getting  colder  and  colder, 
until  at  last  it  reaches  minus  170°  C.1  (which  is  the 
"  boiling  point "  of  liquid  air),  and  after  that  it  comes 
out  liquid. 

As  soon  as  it  is  allowed  to  rise  above  that  tempera- 
ture it  boils,  passing  back  into  vapour  once  more,  and 
the  remarkable  thing  about  it  is  that  the  nitrogen  passes 
off  into  gas  first,  leaving  the  oxygen  behind.  The  last 
gas  which  arises  from  the  liquid  then  is  pure  oxygen, 
and  this  forms  an  easy  means  of  separating  it  from  the 
nitrogen.  After  being  collected  in  this  manner  it  is 
compressed  into  strong  steel  cylinders  for  ease  in  con- 
veying it  about. 

The  subject  of  air  under  pressure  naturally  leads  us 
to  think  of  those  tools  which  are  operated  by  com- 
pressed air.  When  it  is  necessary  to  drill  a  hole  in 
iron  the  best  way  to  do  it  is  to  put  the  piece  of  iron 
under  a  drilling  machine,  and  in  a  very  short  time 
the  hole  will  be  through.  In  this  machine  there  is  a 
vertical  spindle,  driven  round  by  power,  to  the  bottom 
end  of  which  the  drill  is  fixed.  The  work  has  to  be 
held  or  fixed  upon  a  table  under  the  drill,  and  by  turn- 
ing a  handle  the  latter  can  be  brought  down  on  to  it. 
But  suppose  that  the  work  is  so  large,  or  is  so  fixed  that 
it  cannot  be  taken  to  a  drilling  machine.  What  is  to 
be  done  then  ?  One  thing  is  to  drill  it  by  hand,  but 
that  is  a  slow  and  costly  operation.  In  many  cases, 
however,  a  little  pneumatic  drilling  machine,  which  can 
be  carried  in  the  hand,  will  do  it  easily  and  quickly. 

These  little  machines  are  just  like  tiny  steam-engines 
fixed  in  a  small  iron  case  and  driven  by  compressed  air 
instead  of  steam.  They  are  so  small  that  they  can  be 
easily  handled  by  one  man,  and  when  he  wants  to  drill 
a  hole  he  simply  fixes  up  the  little  machine  (which  is 

1  That  is,  nearly  twice  as  much  colder  than  freezing  point,  as  freezing  point 
is  colder  than  boiling  point. 

113  H 


The  Engineer's  Tools 

quite  an  easy  thing  to  do)  and  then  turns  on  the  air, 
when  the  drill  is  driven  round  and  the  hole  soon  made. 
Indeed,  unless  the  hole  is  a  large  one  he  does  not  need  to 
fix  his  machine  at  all,  but  simply  holds  it  in  his  hands. 

It  often  happens,  too,  that  a  piece  of  iron  has  to  be 
trimmed  or  shaped  in  some  way  under  such  circum- 
stances that  it  can  only  be  done  by  chipping  it  with  a 
chisel.  A  man  can  do  this  by  hand,  using  a  chisel  in 
one  hand  and  striking  it  with  a  hammer  held  in  the 
other,  but  that  again  is  a  slow  and  consequently  a 
costly  way  of  doing  it,  and  here  a  compressed-air 
hammer  solves  the  difficulty. 

These  are  called  "  pistol  "  hammers,  because  they  are 
like  a  pistol  in  appearance.  What  corresponds  with 
the  barrel  of  the  pistol  is  really  a  cylinder  in  which  a 
little  block  of  steel  slides  up  and  down  like  a  piston, 
while  at  the  muzzle  end  there  is  a  holder  into  which 
the  chisel  fits.  The  operator  holds  the  hammer  by  the 
handle,  puts  the  point  of  the  chisel  against  the  work, 
and  then  presses  a  little  trigger  which  is  just  under  his 
thumb.  Instantly  the  little  block  of  steel  commences 
to  fly  up  and  down  inside  its  cylinder,  and  every  time, 
of  course,  it  gives  the  chisel  a  sharp  knock  (see  Plate 
opposite).  A  hammer  like  this  will  give  hundreds  or 
even  thousands  of  blows  in  a  minute,  whereas  the  most 
industrious  workman  cannot  do  more  than,  say,  one  per 
second  when  working  with  an  ordinary  hand-hammer. 

In  many  branches  of  engineering,  rivets  play  an  im- 
portant part.  A  boiler,  for  instance,  is  entirely  built  up 
of  steel  plates  riveted  together,  and  the  same  applies  to 
iron  and  steel  bridges  and  ships.  When  rivets  are  put 
in  by  hand  this  is  how  it  is  done. 

Three  men  and  a  boy  work  together  in  a  squad.  Two 
of  the  men  are  skilled  riveters,  and  the  third  is  a  semi- 
skilled man  who  is  called  the  "holder-up,"  while  the 
boy  looks  after  the  little  forge  in  which  the  rivets  are 

114 


fly  permission  of  the 


Consolidated  Pneumatic  Tool  Co.,  Ltd. 


A  PNEUMATIC  HAMMER  AND  CHISEL 


Here  we  see  a  man  using  a  Pneumatic  Hammer  and  Chisel.     He  is  cutting  a  piece  of 
metal  off  the  end  of  a  steel  boiler  flue.     Observe  the  size  of  the  "  shaving." 


The  Engineer's  Tools 

heated.  When  the  men  are  ready  to  put  a  rivet  in  they 
call  to  the  boy,  who  picks  up  a  white-hot  rivet  out  of 
the  fire  with  a  pair  of  tongs  and  throws  it  to  the 
"  holder-up."  The  latter  picks  it  up  with  another  pair 
of  tongs  and  inserts  it  in  the  hole.  He  takes  great 
care  to  push  it  right  in,  and  then  he  holds  a  heavy 
hammer  against  it  while  the  other  riveters  hammer  on 
the  point  of  it  with  lighter  hammers,  taking  alternate 
blows.  When  they  have  knocked  down  the  point  of 
the  rivet  into  the  semblance  of  a  head,  one  of  them 
throws  down  his  hammer  and  snatches  up  another  tool 
called  a  snap.  This  is  like  a  hammer  with  a  cup-shaped 
depression  in  its  face.  He  holds  this  depression  over 
the  partly  formed  head  while  his  mate  flogs  it  as  hard 
as  he  can  with  his  hammer,  and  so  the  nicely  rounded 
heads  such  as  we  see  on  railway  bridges  are  formed. 

Now  in  a  ship,  boiler,  or  bridge  yard,  where  there  is 
a  great  deal  of  riveting,  much  of  it  is  done  by  what 
the  workmen  call  an  "iron  man."  Just  squeeze  a 
pellet  of  bread  or  putty  between  the  thumb  and  first 
finger,  and  you  will  see  exactly  the  way  in  which  an 
"  iron  man  "  squeezes  up  a  rivet.  It  is  just  like  an 
enormous  thumb  and  finger,  large  enough  to  span  over  a 
wide  plate  and  rivet  up  the  joint  on  the  further  edge. 
It  is  worked  by  hydraulic  pressure,  and  is  often  portable, 
being  carried  by  a  crane  specially  used  for  that  purpose. 
A  rivet  is  simply  put  in  the  hole,  the  machine  brought 
into  the  right  position,  a  tap  turned  to  let  in  the  water, 
and  in  an  instant  the  rivet  is  squeezed  up  and  a  stronger 
job  made  than  the  most  skilled  of  hand-riveters  could 
make  in  four  times  the  time.  The  thumb  and  finger 
each  have  a  suitably  shaped  tool,  so  that  the  heads  shall 
be  nicely  formed. 

The  "iron  man,"  however,  is  a  ponderous  machine 
whose  sphere  of  operation  is  consequently  limited,  and 
he  can  only  work  to  advantage  where  there  are  long 


The  Engineer's  Tools 

straight  rows  of  rivets  which  can  be  done  one  after  the 
other  in  quick  succession.  So  for  odd  rivets  and 
rivets  in  awkward  positions  a  pneumatic  pistol-hammer, 
as  described  just  now,  is  often  used,  a  cup-shaped  tool 
being  substituted  for  the  chisel. 

Some  mention  must  be  made  of  that  powerful  tool 
the  steam-hammer.  This  has  a  cylinder  like  that  of  a 
steam-engine  supported  in  a  strong  iron  frame.  In 
the  large  sizes  this  frame  is  virtually  a  strong  iron 
bridge,  with  the  cylinder  in  the  middle,  supported  on 
massive  iron  columns  at  each  end.  The  piston-rod, 
which  is  much  thicker  in  proportion  than  that  of  a 
steam-engine,  carries  at  its  bottom  end  a  heavy  block 
of  iron,  which  forms  the  head  of  the  hammer  ;  immedi- 
ately under  this,  resting  on  the  ground,  is  another  block 
which  forms  the  anvil.  A  small  lever  at  one  side  works 
a  valve  which  controls  the  entrance  of  steam  to  the 
cylinder.  When  this  handle  is  in  one  position  the  steam 
enters  beneath  the  piston  and  lifts  it  up,  taking  with  it 
the  piston-rod  and  head.  In  the  middle  position  of  the 
handle  the  head  is  held  stationary,  and,  in  the  third,  the 
steam  enters  above  the  piston  and  causes  it  to  come 
down  with  a  powerful  blow. 

By  skilful  manipulation  of  the  handle  the  force  of 
the  blow  can  be  regulated  to  such  a  nicety  that  the 
huge  block  of  iron  forming  the  hammer-head  can  be 
made  to  tap  gently,  without  breaking  it,  on  the  shell 
of  an  egg  placed  on  the  anvil. 

As  mentioned  in  the  chapter  on  gas-engines,  there  are 
now  many  works  which  have  no  steam-power  available 
to  work  a  steam-hammer.  In  such  cases  a  pneumatic 
hammer  is  often  used  constructed  on  the  same  principles 
as  a  steam-hammer,  but  worked  with  compressed  air 
instead  of  steam.  There  is  an  air  compressor  combined 
with  the  machine,  which  is  worked  by  the  same  power 
which  drives  the  rest  of  the  machinery  in  the  works. 

116 


The  Engineer's  Tools 

For  many  purposes,  powerful  hydraulic  presses  are 
now  used.  For  example,  the  steel  tubes  of  which 
heavy  naval  guns  are  made  are  forged  out  of  hollow 
ingots  by  means  of  presses.  The  steel  is  made  hot,  and 
is  then  pressed  into  the  desired  form.  In  other  words, 
a  series  of  squeezes  are  substituted  for  the  blows  of  a 
hammer.  Thick  steel  plates,  too,  can  be  pressed  into 
most  fantastic  shapes  by  these  tools,  so  doing  quickly 
and  neatly  work  which  would  be  very  expensive,  if  not 
impossible,  by  any  other  method.  A  simple  example 
of  this  is  the  "  trough  "  flooring  often  used  to  form  the 
floor  of  a  railway  bridge.  A  plate  of  steel  is  heated,  put 
under  a  press,  and  quickly  converted  into  a  deep  trough, 
and -a  number  of  these  troughs,  placed  side  by  side,  con- 
stitute a  floor  strong  enough  to  carry  a  railway  train. 

Another  instance  of  the  use  of  presses  is  in  railway 
vehicles.  It  has  been  found  that  the  best  way  of  fixing 
the  wheels  on  to  the  axles  is  to  make  the  axle  a  "  tight- 
fit"  in  the  hole  in  the  centre  of  the  wheel,  and  then 
force  it  in  by  means  of  a  hydraulic  press,  with  a  pressure 
of  perhaps  50  or  60  tons. 

The  principle  of  these  presses  is  very  simple.  There 
is  a  cylinder  with  a  piston  inside  it,  only  instead  of  the 
latter  being  a  disc,  like  the  piston  of  a  steam-engine,  it 
is  usually  a  solid  block,  and  is  then  known  as  a  "  ram." 
The  water  is  forced  in  by  a  pump  at  a  pressure  of,  say, 
500  Ibs.  per  square  inch,  with  the  consequence  that 
the  "  ram  "  is  pushed  out  of  the  cylinder  with  a  force 
of  500  Ibs.  for  every  square  inch  of  its  area.  Hydraulic 
"  power "  is  not,  really,  a  power  at  all,  but  simply  a 
means  of  concentrating  power.  The  cylinder  of  the 
pump  is  small.  Suppose  it  is  only  i  square  inch  in 
area  ;  the  engine  which  works  it  keeps  on  pressing  the 
ram  of  the  pump  down  with  a  force  of  500  Ibs. ;  that 
pushes  the  water  into  the  cylinder  of  the  press,  which 
may  have  an  area  of  100  square  inches,  with  the  result 

117 


The  Engineer's   Tools 

that  it  will  be  pushed  with  a  force  of  50,000  Ibs.  It 
takes  a  great  deal  more  water,  of  course,  to  fill  the 
press  cylinder  than  it  does  to  fill  the  pump  cylinder, 
and  the  latter  has  to  make  many  strokes  to  every  one 
of  the  former,  so  that  what  is  gained  in  force  is  lost  in 
speed.  There  is  no  real  gain  of  power,  therefore,  in  a 
hydraulic  press,  it  simply  transforms  a  quickly  moving 
weak  force  into  a  slowly  moving  powerful  one. 

This  chapter  might  be  continued  to  an  almost 
indefinite  length,  so  great  is  the  variety  of  appliances 
which  the  engineer  uses  ;  but  there  is  one  machine 
which  must  be  mentioned,  before  concluding,  on 
account  of  its  wide  usefulness.  In  almost  every  works, 
and  particularly  in  shipyards  and  bridge-yards,  it  is 
necessary  to  be  able  to  cut  bars  and  plates  quickly 
and  cheaply  and  also  to  make  holes  in  them,  and  for 
this  purpose  the  punching  and  shearing  machine  is 
most  valuable.  In  its  combined  form  it  has  two  jaws, 
one  for  punching  and  one  for  shearing ;  it  is  worked 
by  a  simple  mechanical  movement,  and  is  usually  driven 
by  a  belt.  The  punching  action  is  exactly  like  that  of 
a  railway-ticket  clipper.  There  is  a  steel  die  with 
a  hole  in  it,  and  exactly  over  this  hole  there  is  a  punch. 
A  steel  plate,  perhaps  an  inch  thick,  is  placed  upon  the 
die,  and  the  punch  comes  down  upon  it,  going  right 
through  the  plate,  and  pushing  a  small  circular  piece 
through  the  die,  from  the  bottom  of  which  it  falls, 
leaving  a  circular  hole  in  the  plate. 

The  shearing  movement  is  a  combination  of  the 
action  of  the  human  jaws  and  a  pair  of  scissors.  One 
jaw  is  fixed  while  the  other  moves  up  and  down,  much 
like  the  jaws  of  an  animal ;  but,  instead  of  meeting  as 
the  teeth  do,  one  jaw  slides  past  the  other  like  the 
blades  of  a  pair  of  scissors.  Thus  they  can  bite  a 
piece  off  a  plate  of  iron  or  steel  as  easily  as  a  pair 
of  scissors  cuts  a  piece  of  thin  card. 

118 


CHAPTER   IX 
BRIDGES 

PROBABLY  one  of  the  earliest  structures  which    man 
learnt  to  make  for  himself  was  a  bridge. 

Its  origin  is  far  back  in  prehistoric  times,  but  it 
seems  probable  that  the  idea  arose  in  some  such  way 
as  this.  Just  imagine  a  tribe  in  the  Stone  Age,  the  sort 
of  people  whose  chipped-flint  tools  are  found  now  in  the 
beds  of  river  gravel,  showing  that  they  lived  by  the 
banks  of  the  rivers.  They  would  most  certainly  want 
at  times  to  get  across  their  river,  and  would  be  forced 
to  ford  or  swim  it.  One  night  there  is  a  storm,  and 
the  next  morning  a  tree  is  found  blown  down  across 
the  stream,  with  its  top  on  one  bank  and  its  roots  on 
the  other.  Even  then,  in  all  probability,  they  do  not 
realise  at  once  all  that  it  means  to  them  ;  but  during  the 
day  the  boys  of  the  tribe  start  playing  on  it,  strip  off 
some  of  the  branches,  and  try  who  can  climb  across  it 
in  the  shortest  time,  until  it  dawns  upon  the  primitive 
intelligence  of  their  elders  that,  there,  is  a  new  and 
convenient  way  of  getting  across  the  water. 

Soon  other  tribes  will  hear  of  it,  and  before  long  will 
find  ways  of  making  trees  fall  across  in  suitable  posi- 
tions, and  so  the  building  of  bridges  becomes  a  regular 
thing. 

Whether  this  fanciful  peep  into  the  remote  past  is 
true  or  not,  there  can  be  no  doubt  that  from  very 
early  times  bridges  have  been  very  important  structures, 
and  to-day  they  are  more  so  than  ever. 

119 


Bridge; 


Modern  bridges  may  be  divided  into  four  kinds, 
arch  bridges,  girder  bridges,  suspension  bridges,  and 
cantilever  bridges. 

Arch  bridges  are  generally  built  of  stone,  brick,  or 
concrete,  but  sometimes  steel  and  iron  are  employed. 

Some  of  the  stone-arch  bridges  are  remarkable  for 
their  beauty.  Waterloo  Bridge  over  the  Thames  in 
London,  for  instance,  is  so  beautiful  that  a  great  Italian 
architect  said  that  it  was  worth  travelling  from  Rome 
to  London  simply  to  see  it.  Bridges  of  the  other  types, 


FIG.  17. — Diagram  showing  the  source  of  strength  in  an  arch. 

however,  are  more  remarkable  for  their  strength  than 
anything  else. 

The  arch  owes  its  strength  to  the  fact  that  the 
shortest  distance  between  two  points  is  a  straight  line. 
In  the  diagram,  Fig.  17,  for  example,  the  shortest 
distance  between  the  two  abutments  is  the  dotted 
line.  If,  then,  we  make  a  curved  structure  like  the 
curved  line  and  place  a  uniform  load  upon  it,  one 
of  three  things  must  happen.  Either  the  material  of 
which  the  arch  is  made  must  be  compressed  until  its 
length  has  been  reduced  to  that  of  the  dotted  line ;  the 
abutments  must  be  pushed  apart ;  or  the  load  will 
remain  supported  upon  the  arch.  It  only  remains, 
therefore,  to  make  the  arch  sufficiently  strong  to  resist 

120 


£y  permission  of  Messrs.  Alfred  Thome  &•  Sons 

THE  "TRANSPORTER"  BRIDGE  AT  NEWPORT  (SOUTH  WALES) 

The  great  girder  is  supported  at  each  end  upon  a  huge  trestle,  one  of  which  can  be 
seen.  On  the  right  we  get  a  glimpse  of  the  trolley  which  travels  on  the  bottom  flanges 
of  the  girder,  from  which  is  suspended  the  car  below. 


Bridges 


the  compression  and  the  abutments  sufficiently 

The  abutments  we  see,  then, 

are   subjected  to   a   push 

or  thrust  sideways  as  well 

as  a  downward  pressure, 

and  that  is  the  distinctive 

feature  of  the  arch. 

Most  bridges  are  simply 
two  girders  (which  is  an- 
other name  for  beams), 
with  a  floor  between.  We 
see  such  girders  carrying 
railways  across  our  roads, 
or  roads  across  railways, 
or  spanning  rivers  and 
valleys.  Some  of  them 
are  very  complicated  structures,  but  in 

they   are  just  the 


rigid. 


FIG.  1 8. — The  simplest  type  of  steel 
beams  or  girders.  These  are  just 
a  solid  piece  of  steel,  rolled  as 
described  in  Chapter  VI.  They 
are  much  used  in  the  framework 
of  buildings.  They  are  generally 
called  rolled  steel  joists. 


Top 


the  familiar 
which   we  see  in 
supported    at    its 
two    brick    walls 
a  roof  or  floor. 


principle 
same   as 
beam  of  wood 
a   house, 
ends    on 
to    carry 
They  are 


BoltOW  Flany 


FIG.  19.— This  is  a  "  Plate  Girder." 
A  vertical  plate  forms  the 
"web,"  and  each  flange  con- 
sists of  one  or  more  plates. 
The  flanges  are  connected  to 
the  web  with  "angle  irons," 
and  all  are  riveted  together. 


generally  built  up  of  iron 
or  steel  plates  and  bars 
riveted  together;  a  material 
known  as  ferro-concrete  is 
now  coming  into  use  for 
such  purposes,  but  that  will 
be  referred  to  in  a  later 
chapter. 

Suspension  bridges  are  on 
quite  a  different  principle. 
They  are  supported  by  tall 
towers,  from  the  top  of 


which  depend  strong  steel   cables,  or  chains  built  up 

121 


Bridges 


of  plates  of  steel,  and  from  these  cables  or  chains  the 
bridge  itself  is  suspended. 

Of  cantilever  bridges  perhaps  the  best-known  example 
is  the  famous  structure  across  the  Firth  of  Forth  in 
Scotland.  It  may  be  likened  to  several  men  standing  in 
a  row  and  extending  their  arms  out  towards  one  another. 
Each  outstretched  arm  is  a  cantilever.  Another  way 
to  describe  a  cantilever  is  to  say  that  while  a  beam  is 
supported  at  each  end,  and  has  its  load  in  between,  a 
cantilever  is  supported  at  one  end  only.  Every  bracket 
fixed  to  a  wall,  a  common  object  in  most  houses,  is  a 
cantilever. 

The  cantilever  principle  plays  a  very  important  part 
in  the  construction  of  theatres  and  public  halls  nowa- 


FIG.  20. — This  is  a  "Lattice  Girder."  The  flanges  are 
built  up  of  plates  and  angles,  as  in  a  plate  girder,  but 
instead  of  the  solid-plate  web,  there  is  a  system  of  struts 
and  ties. 

days.  In  old  halls  the  galleries  are  supported  upon 
columns  which  often  seriously  interfere  with  the  view 
of  the  audience  ;  but,  in  modern  buildings  of  that  de- 
scription, the  galleries  seem  to  be  supporting  themselves 
and  everyone  has  a  clear  view.  The  secret  of  the 
structure  is  that,  hidden  beneath  the  floor,  there  are 
powerful  steel  cantilevers  firmly  fixed  in  the  walls,  so 
that  they  are  capable  of  supporting  the  whole  weight 
of  the  gallery  and  its  occupants  without  the  assistance 
of  columns  at  all.  How  it  is  arranged  can  be  seen  in 
Fig.  21. 

The  designing  of  a  bridge  used  to  be  a  matter  of 
judgment  only.  The  designer  made  the  parts  as  strong 
as  they  seemed  to  him  to  need  to  be,  and  his  judgment 

122 


Bridge! 


was  verified  afterwards  by  each  part  being  tested  with 
heavy  weights  before  it  was  erected.  Now,  however, 
the  underlying  principles  are  so  well  understood  that 
the  requisite  strength  of  each  part  can  be  calculated 
out  with  great  accuracy  upon  paper.  In  complex  struc- 
tures this  is  by  no  means  an  easy  thing  to  do,  and  a 
competent  bridge^draughtsman  needs  to  be  a  pretty  good 
mathematician.  Many  of  the  necessary  calculations 
have,  however,  been  boiled  down  into  short  convenient 
formulae  easy  to  remember  and  to  work  out.  Just  one 


Gallery 
Floor 


FIG.  21. — This  shows  how  the  galleries  in  modern  public 
buildings  are  supported  from  the  walls  by  means  of 
cantilevers. 

simple  instance  of  this  may  be  of  interest.  A  girder  is 
generally,  if  viewed  as  though  cut  through  the  centre, 
the  shape  of  a  capital  letter  I,  and  the  horizontal  parts 
at  the  top  and  bottom  are  called  the  "  flanges,"  while 
the  vertical  part  is  known  as  the  "  web."  Now  the 
action  of  the  load  is  to  compress  the  top  flange  inwards 
towards  the  centre,  and  to  pull  the  bottom  one  outwards 
from  the  centre,  the  web  connecting  the  two  together 
and  preventing  them  from  moving  in  relation  to  each 
other.  An  important  problem,  therefore,  is  to  find  out 
what  the  push  or  pull  will  amount  to  in  order  that  the 
flanges  may  be  made  sufficiently  strong.  This  is  told 

123 


Bridges 


by  a  formula  which  is  usually  written  down  like 
this— 

W     L 

8      D 

which  means  that  if  we  multiply  the  weight  (W)  which 
will  come  on  the  girder  by  the  length  of  the  girder  (L), 
and  then  divide  the  result  by  eight  times  its  depth  (D), 
we  shall  get  what  we  want — namely,  the  pull  in  the 
bottom  flange  and  the  push  in  the  top. 

Another  way  in  which  the  labour  of  elaborate  calcu- 
lations is  saved  is  by  diagrams.  A  calculation  which 
would  need  great  mathematical  skill,  and  take  consider- 
able time  to  work  out  by  figures,  can  often  be  done 
easily  and  in  a  few  minutes  by  means  of  a  diagram. 

The  load  which  a  bridge  is  designed  to  carry  is  the 
utmost  that  it  would  be  possible  (not  merely  probable) 
by  any  combination  of  circumstances  to  get  upon  it. 
For  example,  if  it  be  a  railway  bridge,  it  is  assumed  to 
be  covered  with  as  many  of  the  heaviest  locomotives 
as  can  be  crowded  together,  or,  if  it  is  a  foot-bridge,  it 
is  assumed  to  be  covered  with  a  dense  mass  of  people. 
Then,  when  the  maximum  possible  load  has  been 
allowed  for,  the  bridge  is  made  about  five  times  as 
strong  as  would  carry  it,  or,  to  use  the  technical  phrase, 
a  "  factor  of  safety  of  5  "  is  used. 

When  a  bridge  is  designed  its  main  features  are 
decided  upon  by  the  chief-engineer,  and  then  (in 
England)  he  sets  a  large  staff  of  skilled  draughtsmen 
to  work  out  the  details  under  his  supervision.  Many 
sheets  of  drawings  are  thus  produced,  giving  even  the 
minutest  details.  After  that,  the  "  quantities "  are 
reckoned  out — that  is  to  say,  the  exact  weight  of  steel 
of  each  description,  the  number  of  cubic  yards  of  ex- 
cavation and  concrete  in  the  foundations,  the  quantity 
of  brick-work,  stone-work,  wood-work,  and  so  on, 

124 


Bridges 

often  forming  a  schedule  many  pages  in  length.  Then 
a  specification  is  drawn  up  stating  exactly  what  qualities 
the  various  materials  must  be,  the  tests  which  they  are 
to  stand,  and  the  conditions  under  which  the  work 
must  be  carried  out.  Finally,  these  three,  the  draw- 
ings, the  schedule  of  quantities,  and  the  specification, 
are  sent  to  the  contractors  to  make  up  their  tenders 
upon,  and  when  a  tender  is  accepted  they  become  the 
basis  of  the  contract. 

In  America  the  details  are  left  to  the  contractor  to 
design  for  himself,  so  that  he  may  make  them  to  suit 
his  plant,  subject  of  course  to  the  engineer's  approval. 

Certainly  not  the  least  important  part  of  a  bridge 
is  the  foundations,  and  they  are  frequently  the  most 
difficult  part  to  construct,  especially  when,  as  is  often 
the  case,  they  are  in  deep  water.  An  example  of  this 
kind  of  work  recently  occurred  during  the  building  of 
the  new  part  of  Blackfriars  Bridge  over  the  Thames  in 
London. 

The  difficulty,  of  course,  is  to  get  the  water  out  of 
the  way,  and  to  keep  it  so  until  the  foundations  can  be 
constructed.  This  is  often  done  by  sinking  a  "  caisson," 
as  it  is  called,  a  large  iron  box,  inside  which  the  work 
can  be  carried  on  and  which  will  itself  ultimately  form 
part  of  the  foundations. 

In  the  case  referred  to,  a  strong  stage  was  first 
made  by  driving  timber  piles  into  the  bed  of  the  river, 
leaving  a  large  open  space  in  the  middle  of  it  for  the 
caisson  to  be  lowered  down. 

The  caisson  was  built  up  of  steel  plates  connected  by 
rivets,  and  was  put  together  on  this  staging  so  that,  when 
it  was  ready,  it  could  be  let  down  the  space  on  to  the 
bed  of  the  river.  About  half-way  down  a  caisson  there 
is  a  steel  floor,  and  above  that  is  placed  a  quantity  of 
concrete  in  order  to  make  it  heavy  enough  to  sink  in 
the  water. 

125 


Bridges 


When  all  is  ready,  the  caisson  is  lowered  by  means 
of  hydraulic  jacks  on  to  the  river-bed,  and  its  lower 
edge  being  sharp,  it  cuts  its  way  into  the  soft  mud.  In 
the  floor  of  the  caisson  there  is  a  hole,  and  a  steel  pipe 
is  connected  to  it,  coming  up  through  the  concrete  to 
well  above  water-level.  At  the  top  of  this  pipe  or  shaft 


Airtiaht 

Steet 
Cy/mder 


Steel  fioo 


AirUcfi^ 

Air-tight 

J  Shaft  fo 
to  yo  uf. 

uj.it  h  Air 
The  top  * 

>Steet 
r  men 
i  or  do  tun 
-Lock  at 

'/*  (4  • 

Concrete 

fomaKz 
itsmH 

Workmy  Chamber 

V-  Open  here  and  with 
a  sharp  edye  a// 
round 

FIG.  22. — Diagram  showing  construction  ol  a  Caisson, 
for  building  foundations  in  deep  water. 

there  is  an  air-lock,  an  arrangement  of  doors  which 
enable  men  and  buckets  of  dirt  to  be  passed  through 
without  allowing  any  air  to  escape.  When,  therefore, 
the  caisson  has  settled  down  as  far  as  it  will  go  of  its 
own  weight,  these  doors  are  kept  closed,  and  air  is 
pumped  into  the  shaft  so  as  to  keep  the  water  out  of 
the  caisson  while  men  go  down  and  shovel  away  the 
dirt  out  of  the  inside.  As  this  goes  on  the  caisson 

126 


Bridges 


gradually  settles  down  farther  and  farther,  until  it 
reaches  a  hard  stratum,  capable  of  furnishing  a  good 
foundation.  Then  the  whole  of  the  bottom  chamber 
is  filled  with  concrete,  and  the  shaft  as  well,  so  that  it 
becomes  a  huge  block  of  concrete  encased  in  steel. 
The  piers  of  the  bridge,  of  stone  or  whatever  they  may 
be,  are  then  built  up  on  the  caisson,  and  finally  the 
piles  are  drawn  out. 

It  is  clear  that  the  main  feature  of  this  operation  is 
the  compressed  air,  which  keeps  the  water  from  entering 
the  open  end  of  the  caisson  while  the  men  are  at  work 
there  ;  it  is  a  most  convenient  and  effective  way  of 
doing  the  work,  but  sometimes  it  can  be  done  just  as 
well  without  the  compressed  air.  Only  recently  a 
bridge  was  erected  in  the  Straits  Settlements  which 
well  illustrates  this  method. 

In  this  case  the  bridge  is  supported  upon  iron 
cylindrical  pillars  fixed  in  the  bed  of  the  river.  The 
cylinders  are  about  eight  feet  in  diameter,  and  are  made 
in  short  sections  which  can  be  bolted  together  so  as  to 
form  any  length  required.  The  lower  sections  are 
made  of  steel,  but  the  part  which  is  above  the  lowest 
tide-level  is  made  of  cast  iron,  because  iron  or  steel 
which  is  alternately  wet  and  dry  is  very  subject  to  rust, 
much  more  so  than  when  it  is  always  wet,  and  cast 
iron  resists  rusting  much  better  than  steel  does. 

First  of  all  a  light  temporary  bridge  was  made  of 
steel  piles  driven  into  the  bed  of  the  river.  The  first 
intention  was  to  use  screw-piles  such  as  are  often  used 
to  support  seaside  piers.  These  are  long  iron  or  steel 
columns,  with  a  large  screw-thread  on  one  end,  and 
they  are  put  down  into  the  bed  of  the  river  and  then 
screwed  round,  and  so  driven  into  the  ground  just  as 
a  carpenter  drives  a  screw  into  a  piece  of  wood.  In 
this  case,  however,  it  was  found  that  the  mud  was  so 
soft  that  the  screw  simply  stirred  up  a  large  muddy 

127 


Bridges 


«  puddle  "  and  made  no  progress  at  all,  or  it  might  be 
expressed  by  saying  that  the  thread  of  the  screw  would 
not  bite  in  the  soft  mud. 

The  screw-threads  were  done  away  with,  therefore, 
and  a  sharp  point  put  on  instead,  after  which  they 
could  be  driven  by  a  pile-engine  just  as  timber-piles 
are  usually  driven.  This  is  such  a  common  occurrence 
that  most  of  my  readers  have  probably  seen  it  in  opera- 
tion, but  as  there  may  be  some  who  have  not,  I  ought 
perhaps  to  give  just  a  brief  description.  A  pile-driver, 
or  pile-engine  as  it  is  sometimes  called,  consists  of  a 
vertical  wooden  frame  in  which  slides  a  heavy  block  of 
iron,  called  a  monkey.  At  the  top  of  the  ft  monkey  " 
there  is  a  clip  to  which  a  rope  is  attached  so  that  it 
can  be  wound  up  by  means  of  a  winch  to  the  top  of 
the  frame,  and  no  doubt  it  is  this  climbing  action 
which  has  earned  it  the  name  of  "  monkey."  As  soon 
as  it  reaches  the  top  the  catch  is  released  either  by  the 
pulling  of  a  string,  or  in  some  other  convenient  way, 
and  then  the  monkey  falls.  The  machine  is  so  placed 
that  the  monkey  falls  upon  the  head  of  the  pile  and 
drives  it  in  with  an  action  exactly  analogous  to  that  of 
a  hammer  and  nail.  When  there  are  a  good  number 
of  piles  to  be  driven,  a  steam-winch  is  generally  used, 
but  where  there  are  only  a  few  it  is  done  by  hand. 

After  a  temporary  bridge  had  been  constructed  of 
piles  driven  in  this  manner,  sections  of  iron  cylinders 
which  were  to  form  the  pillars  of  the  permanent  bridge 
were  taken  out  upon  it  to  the  spot  where  they  were  to 
be  sunk,  and  several  were  put  together  and  lowered 
on  to  the  river  bed.  The  edge,  which  was  sharp,  at 
once  cut  its  way  into  the  mud  to  a  distance  of  several 
feet,  and  the  whole  thing  was  heavily  weighted  until  it 
had  gone  as  far  down  as  it  would.  Then  a  pump  was 
set  to  work  to  empty  the  water  out  of  the  inside  ;  for, 
observe,  it  had  no  floor  such  as  a  caisson  has,  being 

128 


By  kind  permission  ofj.  y.  Webster,  Esq.,  M.Inst.C.E. 


A  yo-ToN  BRIDGE  TAKING  A  RIVER  TRIP 

This  photograph  shows  a  bridge,  weighing  70  tons,  being  carried  down  the  River 
Mersey  by  a  floating  crane.  The  crane,  which  belongs  to  the  Mersey  Harbour  Board, 
could  have  taken,  comfortably,  another  30  tons,  as  it  is  designed  to  lift  100  tons. 


Bridges 

simply  a  large  pipe,  and  when  it  was  emptied  of  water 
by  a  pump  it  was  found  that  the  clay,  into  which  it  had 
penetrated  some  distance,  made  a  sufficiently  good 
watertight  joint  against  the  metal  pipe  to  permit  men 
to  go  down  and  clear  out  the  mud  and  clay  which  was 
inside.  As  that  operation  went  on  the  huge  cylinder 
sank  lower  and  lower,  until  it  reached  the  solid  rock 
under  the  clay.  In  this  way  the  cylinders  were  sunk 
to  a  depth  of  about  eighty  feet. 

When  the  rock  had  been  reached,  the  inside  of  the 
cylinder  was  filled  with  concrete,  and  a  fine  strong 
foundation  upon  the  solid  rock  was  the  result. 

Reverting  for  a  moment  to  the  question  of  driving 
piles,  there  is  a  method  which  is  used  sometimes  which 
is  interesting  on  account  of  the  fact  that  it  would  not 
appear  on  the  face  of  it  to  be  at  all  likely  to  be  effec- 
tive. It  can  only  be  used  when  the  pile  has  to  be 
fixed  in  sand. 

We  have  been  taught  to  regard  a  man  who  lays  his 
foundations  upon  sand  as  an  example  of  folly,  and  no 
doubt  such  was  the  case  in  the  state  of  the  building  art 
at  the  time  when  the  saying  upon  which  this  is  founded 
was  first  uttered.  With  modern  methods,  however, 
sand  can,  if  treated  properly,  be  made  to  furnish  a 
very  good  foundation,  for  if  dry  or  uniformly  wet  it  is 
very  solid  and  firm — very  different  from  wet  clay,  for 
instance,  which  if  wet  will  allow  anything  standing 
upon  it  to  slide. 

It  is  possible,  therefore,  to  fix  a  pile  very  firmly  in 
sand,  and  it  can  be  done  in  this  simple  way.  Inside 
the  pile  a  small  pipe  is  fitted,  through  which  water  is 
pumped,  the  water  issuing  as  a  strong  jet  at  the  bottom. 
As  the  pile  is  lowered  this  jet  blows  its  way  through 
the  sand,  stirring  it  up  so  that  the  pile  can  be  let  down 
quite  quickly.  Then,  when  it  has  gone  far  enough,  the 
small  pipe  is  withdrawn,  and  the  sand  settles  back  all 

129  I 


Bridges 


round  the  pile,  so  that  in  a  very  short  time  it  is  quite 
solid  again,  and  the  pile  is  quite  firm. 

Another  way  of  building  foundations  in  water  is  by 
what  is  called  a  "  cofferdam."  This  consists  of  a 
number  of  piles  driven  in  near  together  with  boarding 
between,  the  interstices  being  afterwards  stopped  up 
with  clay  or  some  other  impervious  material.  That 
constitutes  a  waterproof  wall  from  behind  which  the 
water  can  be  pumped  out,  and  then  the  work  can 
proceed.  This  plan  is  often  used  where  the  water  is 
not  very  deep,  or  where  it  is  tidal  and  the  part  wihere 
the  work  has  to  be  done  is  dry  at  low  tide. 

The  embankment  wall  in  front  of  the  new  County 
Hall  in  London  is  built  under  the  protection  of  a 
"  cofferdam  "  constructed  in  this  way. 

Perhaps  the  most  important  bridge  built  in  recent 
years  is  the  Blackwells  Island  Bridge,  across  the  East 
River  in  New  York.  The  length  of  the  largest  span 
is  second  only  to  that  of  the  Forth  Bridge,  and  in 
other  respects  this  bridge  is  unapproached.  It  is 
estimated  that  it  will  carry  200,000,000  tramcar  pas- 
sengers every  year,  besides  many  millions  of  pedestrians 
and  carts. 

It  is  over  1 200  yards  long,  and  is  a  two-deck  arrange- 
ment, the  lower  one  carrying  a  wide  carriage  way  and 
four  car  tracks,  while  the  upper  deck  carries  four 
elevated  railroad  tracks  and  two  wide  promenades  for 
foot  passengers.  The  steelwork  alone  weighs  over 
50,000  tons,  and  it  cost  about  $20,000,000  or 
^5,000,000.  Altogether  it  is  clearly  one  of  the  greatest 
structures  that  man  has  ever  created. 

It  is  of  the  cantilever  type,  the  great  advantage  of 
which  is  that  it  can  be  erected  easily.  It  often  happens 
with  bridges  that  they  are  easy  to  make  but  extremely 
difficult  to  put  up.  Suppose,  for  example,  that  this  had 
been  a  girder  bridge  ;  the  largest  girder  would  have 

130 


Bridges 

had  to  be  over  noo  feet  long,  and  it  would  have  been 
necessary  to  build  a  temporary  stage  or  bridge,  on 
which  to  put  this  huge  girder  together,  or  else  to  put 
it  together  elsewhere  and  then  hoist  it  up  into  position. 
Now  engineers  can  do  many  wonderful  things,  but 
either  of  those  methods  is  almost  beyond  their  powers, 
especially  on  a  busy  tidal  river.  A  girder  bridge  is 
out  of  the  question,  therefore,  and  the  suspension 
principle  is  not  suitable  for  such  a  very  heavy  structure. 
Against  this  put  the  ease  with  which  the  cantilever 
structure  can  be  built  up.  Each  pair  of  cantilevers 
actually  meet  in  the  middle  of  the  span,  but  they  do 
not  depend  for  their  stability  upon  that  fact,  since 
they  derive  their  strength  entirely  from  their  ends. 
It  is  quite  safe,  therefore,  to  start  at  the  ends  and  build 
outwards,  piece  by  piece,  the  part  already  completed 
forming  a  stage  upon  which  the  next  piece  can  be 
brought  out  and  put  in  place. 

In  most  bridges  of  this  kind  there  is  a  small  girder 
supported  between  the  two  adjacent  ends  of  the  canti- 
levers, which  forms  an  adjustable  filling-in  piece,  but 
in  this  case  each  pair  of  cantilevers  actually  join  up 
into  one,  and  so  the  preliminary  measurements  had  to 
be  very  exact,  otherwise  they  would  not  have  met 
properly.  As  a  matter  of  fact  all  the  steelwork  was 
made  at  a  bridgeworks  many  miles  away  and  brought 
to  the  site  all  ready  to  be  put  together,  yet  so  exact 
were  the  measurements  that  when  the  two  arms  met  in 
the  middle  of  the  channel  the  steelwork  came  almost 
exactly  right,  and  scarcely  a  thing  had  to  be  altered. 

It  is  easy  to  see  that  this  depended  entirely  upon  the 
distance  across  the  water  being  measured  accurately  to 
within  a  small  fraction  of  an  inch.  Consider  for 
a  moment  what  that  means.  To  measure  with  such 
accuracy  as  that  across  a  waterway  over  a  thousand  feet 
wide  !  How  can  it  be  done  ?  A  steel  wire  might  be 


Bridges 

stretched  across  and  then  measured  afterwards,  but  that 
would  sag  in  the  middle  ;  it  would  stretch,  too,  with  its 
own  weight,  and  there  would  be  considerable  variation 
in  it  with  the  changes  in  temperature.  That,  then, 
would  not  be  sufficiently  true  for  the  purpose.  Let  us 
see  how  it  was  done. 

The   method   adopted  is   what  is  called  "triangula- 
tion,"  and  it  is  additionally  interesting  in  that  it  is  the 

land 


Island 


Land 

FIG.  23. — Taking  an  exact  measurement  across  water. 

The  two  parts  of  the  base  line  I  and  2  are  first  measured  with  scrupulous 
care.  Then  the  angles  A  and  B  are  observed  with  a  theodolite,  and,  as  a 
check,  the  angle  C  too.  From  that  the  length  of  the  line  3  can  be  calcu- 
lated. This  is  again  checked  by  observing  the  angles  D,  E,  and  F. 

Line  4  can  be  measured  in  an  exactly  similar  way,  by  means  of  angles 
G,  H,  and  J,  and  K,  L,  and  M. 

method  by  which  all  surveying  is  done  and  by  which 
accurate  maps  are  produced.  It  is  on  the  same 
principle,  too,  that  the  distances  of  the  heavenly  bodies 
are  found. 

It  is  based  upon  the  fact  that  if  we  know  the  length 
of  one  side  of  a  triangle,  and  the  number  of  degrees  and 

132 


SURVEYING  UNDER  DIFFICULTIES 

This  striking  picture  represents  men  surveying  for  a  new  railway.  The  line  will  have 
to  run  on  a  ledge  cut  in  the  face  of  the  cliff,  and  the  surveyors  are  here  shown  examining 
the  rocks  and  measuring  the  heights  and  levels  so  as  to  determine  the  best  course  for 
the  cutting. 


Bridges 

parts  of  a  degree  in  the  angle  at  each  end  of  that  line, 
we  can  calculate  the  length  of  the  other  two  sides. 

As  the  illustration  shows,  the  two  middle  supports 
are  on  an  island  between  the  two  channels,  and  on  this 
island  a  line  was  measured  to  form  the  base  of  the 
triangle.  This  line  was  1671.03  feet  long,  and  it  was 
measured  with  a  steel  tape  200  feet  long.  This  was 
first  of  all  checked  by  the  Government  Standards 
Department,  and  found  to  be  correct  at  a  certain 
temperature  and  when  subjected  to  a  pull  of  12 £  Ibs. 
It  was  then  laid  down,  supported  on  pegs  at  every 
25  feet,  and  carefully  pulled  to  exactly  the  weight  of 
12 1  Ibs.,  which  was  sufficient  to  pull  it  quite  straight. 
Each  time  it  was  used  the  temperature  was  taken, 
and  the  measurement  which  it  showed  was  carefully 
corrected  accordingly.  If  the  temperature  was  above 
that  at  which  it  was  tested  something  was  added, 
or  if  it  was  lower  something  was  deducted,  so  as 
to  obtain  the  utmost  accuracy.  Three  times  the  line 
was  measured  like  this,  and  the  results  only  showed 
a  variation  of  about  one-fortieth  of  an  inch. 

Each  end  of  the  line  was  marked  by  a  small  hole 
drilled  in  a  brass  plate  fixed  upon  a  granite  pillar. 

Then  the  angles  were  measured  with  a  theodolite. 
This  is  a  telescope  mounted  on  a  strong  tripod  stand. 
It  can  be  pointed  in  any  direction,  and  there  are  scales 
and  graduated  circles  attached  to  it,  by  means  of  which 
its  exact  direction  can  be  determined.  It  is  first  set  up 
and  sighted  upon  an  object ;  then  it  is  swung  round 
and  sighted  on  a  second  one,  and  the  amount  that  it 
has  to  be  moved  (which  can  easily  be  read  off  the 
graduated  scale)  shows  the  angle  formed  by  straight 
lines  drawn  from  it  to  the  two  objects. 

A  theodolite,  therefore,  was  set  up  at  one  end  of 
the  line  and  sighted  upon  a  rod  set  up  at  the  other  end, 
and  then  upon  another  rod  set  up  on  the  opposite 

133 


Bridges 


bank,  and  so  the  angles  at  the  end  of  the  base  line  were 
determined,  and  from  that  the  distance  of  the  rod  on 
the  opposite  bank  could  be  calculated. 

As  a  matter  of  fact,  to  ensure  accuracy  the  base  line 
was  divided  into  two,  and  two  triangles  were  constructed 
on  each  side  of  it,  as  shown  in  the  diagram  (Fig.  23).  Thus 
eight  angles  were  measured  on  the  island,  and  then  the 
theodolite  was  taken  to  the  mainland  and  two  angles 
measured  on  each  bank,  making  twelve  in  all,  and  they 
were  all  measured  a  hundred  times  over,  and  the  mean 
of  the  measurements  taken,  so  as  to  eliminate  errors. 
It  will  be  seen  that  each  pair  of  triangles  has  one  side 
in  common,  so  that  they  check  each  other,  and  that  the 
two  triangles  of  each  pair  are  reckoned  from  two 
different  parts  of  the  base  line,  so  that  they  too  are 
checked  one  against  the  other. 

I  have  gone  at  some  length  into  this  description 
since  it  is  a  remarkable  feat  of  measuring,  and  shows 
the  extreme  care  which  has  to  be  taken  in  work  of  this 
kind.  Most  of  us  think,  if  we  measure  a  thing  a  few 
feet  long  accurately  within  about  a  sixteenth  of  an  inch, 
that  we  have  been  very  particular.  What,  then,  are  we 
to  think  of  a  length  of  over  a  thousand  feet  measured 
to  within  a  fiftieth  of  an  inch  ? 

The  actual  making  of  the  steelwork  of  a  bridge  is 
not  a  very  interesting  operation.  The  parts  are  first  of 
all  set  out  or  drawn  full  size  on  a  large  wooden  floor, 
and  a  model  or  template  is  made,  in  thin  wood,  of  each 
piece  of  iron  or  steel.  Then  the  plates  or  bars  are  cut 
to  the  same  size  and  shape  as  the  wood  templates,  and 
the  holes  are  either  drilled  or  punched  in.  The  pieces 
are  then  assembled  together  and  connected  temporarily 
with  a  few  bolts,  after  which  rivets  are  put  in  and  the 
work  is  then  finished. 

When  a  bridge  is  over  a  waterway  along  which  tall 
ships  have  to  pass,  it  generally  has  to  be  made  to  open 

134 


Bridge; 


in  some  way.  The  Tower  Bridge  over  the  Thames  in 
London  is  a  well-known  example  of  this.  Its  main 
span  consists  of  two  hinged  cantilevers,  called  "  bas- 
cules," which  can  be  raised  into  a  nearly  vertical 
position  when  a  ship  needs  to  pass  through. 

Of  "  swing "  bridges,  one  part  of  which  is  made  to 
swing  open  like  a  gate,  there  are  innumerable  examples, 
but  a  very  remarkable  one  near  Manchester  deserves 
special  mention.  When  the  first  canal  in  England  was 
constructed  (now  known  as  the  Bridgewater  Canal)  it 
had  to  be  carried  across  the  river  Irwell,  and  at  that 
time  its  promoters  were  thought  by  the  public  to  be 
mad  even  to  entertain  the  idea  of  carrying  a  canal  on  a 
bridge  over  a  river.  They  did  it  successfully;  however, 
and  when  the  Irwell  at  that  point  was  converted  into 
the  Manchester  Ship  Canal,  the  engineers  went  "  one 
better  "  still,  for  they  pulled  the  old  bridge  down,  and 
now  the  Bridgewater  Canal  crosses  the  Ship  Canal  on  a 
swing  bridge.  There  are  gates,  of  course,  at  each  end 
of  the  bridge,  and  also  at  the  ends  of  the  canal  itself, 
and  when  a  ship  wants  to  pass,  these  gates  are  closed 
and  the  bridge,  with  the  water  in  it,  is  swung  round. 

There  is  a  small  but  rather  curious  opening  bridge, 
over  one  of  the  docks  in  London.  It  carries  a  road 
over  one  of  the  basins,  and  as  there  is  not  room  for  it 
to  swing  it  is  arranged  so  that,  to  open,  it  rises  up  off 
its  supports  and  slides  off  up  the  road.  The  first  time  I 
saw  it  I  happened  to  be  approaching  just  as  it  was 
opening,  and  I  was  no  little  astonished  to  see  a  bridge 
apparently  coming  along  the  road  to  meet  me. 

Opening  bridges  are  in  many  cases  worked  by 
hydraulic  power,  but  in  the  more  recent  ones,  electric 
motors  are  generally  used. 

There  is  also  a  new  type  of  bridge  for  use  across 
navigable  rivers,  known  as  "  transporter  bridges,"  of 
which,  as  far  as  I  know,  there  are  only  three  or  four 


Bridges 

examples  yet  in  existence.  Over  each  bank  there  is  a 
tall  steel  tower,  supporting  the  ends  of  a  large  girder  at 
a  level  sufficiently  high  for  the  tallest  mast  of  a  ship  to 
pass  under  it.  On  the  girder  there  runs  a  carriage  or 
trolley,  from  which  there  is  suspended  a  large  platform. 
The  carriage  can  be  pulled  to  and  fro  by  means  of 
electric  motors.  The  passengers  and  vehicles  get  on 
the  platform  when,  it  is  close  to  the  bank,  and  are  then 
carried  across  to  the  other  side.  It  is  really  like  a 
ferry-boat  suspended  from  a  bridge  overhead  instead 
of  supported  on  the  water  below. 


136 


CHAPTER   X 

IRON  AND  STEEL  SHIPS 

MERCHANT  steamships  may  be  divided  into  three 
classes — those  which  are  built  primarily  for  passengers, 
those  which  are  mainly  cargo  steamers  but  which 
carry  passengers  as  well,  and  those  which  only  carry 
cargo,  and  have  no  passenger  accommodation  at  all. 

These  last,  though  often  spoken  of  contemptuously  as 
"  ocean  tramps,"  are  really  of  the  utmost  importance, 
for  they  carry  the  great  staple  commodities  on  which 
so  much  depends — the  grain  and  the  coal,  the  oil  and 
the  timber.  They  are,  therefore,  well  worthy  of  our 
consideration. 

A  trip  round  any  busy  seaport  will  show  the  reader, 
if  he  has  not  noticed  it  already,  that  there  are  many 
different  types  of  the  ordinary  cargo  steamer.  The 
feature  which  displays  the  differences  most  noticeably 
is  the  arrangement  of  the  structures  upon  the  deck,  and 
it  may  reasonably  be  asked  why  there  are  these  varieties, 
and  how  it  is  that  a  common  type  has  not  come  to  be 
agreed  upon. 

The  answer  to  that  question  is  that  the  differences 
are  not  merely  arbitrary,  but  are  due  to  a  variety  of 
influences,  and  it  will  be  interesting  to  look  briefly  at 
these,  as  the  reader  will  then  be  able,  the  next  time  he 
sees  a  cargo  steamer,  to  understand  something  of  the 
ideas  underlying  its  design. 

The  early  steamers  had  "  flush  "  decks,  which  means 
that  the  deck  ran  from  end  to  end  without  any  struc- 

137 


Iron  and  Steel  Ships 

tures  of  considerable  size  upon  it  ;  a  light  bridge  was 
provided,  supported  upon  slender  uprights,  for  tl  look- 
out "  purposes,  and  that  was  about  all.  On  the  face  of 
it,  this  seems  a  very  simple  and  admirable  arrangement. 
It  had  many  disadvantages,  however,  as  we  shall  see. 

In  the  first  place,  it  permitted  a  wave  to  come  on 
board  at  the  bow  and  sweep  right  along  the  deck,  often 
doing  great  damage.  This  was  mitigated  somewhat  by 
building  the  ships  with  "  shear,"  that  is,  with  a  slope 
upwards  fore  and  aft,  so  as  to  make  the  ends  taller 
than  the  middle.  That,  however,  was  not  sufficient,  so 
ships  were  built  with  an  upper  deck,  so  that  the  bow 
should  be  high  enough  to  cut  through  the  waves 
instead  of  allowing  the  water  to  come  on  board. 
Owing,  however,  to  the  method  by  which  the  tonnage 
of  a  ship  is  reckoned,  as  will  be  explained  later,  that 
had  the  effect  of  adding  largely  to  the  tonnage  on  which 
dues  have  to  be  paid  without  materially  increasing  the 
carrying  capacity  of  the  ship. 

The  difficulty  was  therefore  got  over  in  this  way. 
The  bow  was  raised  and  covered  in,  forming  what  is 
known  as  a  "  top-gallant  forecastle,"  which  not  only 
had  the  effect  of  keeping  the  water  off  the  deck,  but 
provided  better  accommodation  for  the  crew  as  well. 
That  did  not  provide,  however,  against  a  wave  over- 
taking the  ship  in  the  rear  and  coming  on  board  just 
where  the  steering  wheel  was,  so  a  hood  or  cover  over 
the  wheel  became  usual,  called  the  "  poop."  Nor  did 
either  of  these  sufficiently  protect  that  very  important 
point,  the  engine-room.  For  it  needs  but  a  moment's 
thought  to  see  that  there  must  be  openings  in  the  deck 
over  the  engines  and  boilers,  and  if  a  volume  of  water 
should  get  down  these,  it  might  extinguish  the  fires  and 
leave  the  ship  helpless,  absolutely  at  the  mercy  of  the 
waves.  The  light  navigating  bridge  was  therefore 
developed  into  a  substantial  structure  the  whole  width 

138 


Iron  and  Steel  Ships 

of  the  ship,  surrounding  and  protecting  the  engine-  and 
boiler-room  openings,  and  incidentally  providing  ac- 
commodation for  the  officers. 

Ships  of  this  type  answered  very  well  indeed,  for  if  a 
wave  of  exceptional  size  should  manage  to  get  over  the 
forecastle,  the  water  fell  into  the  "  well "  or  space 
between  the  forecastle  and  the  bridge-house,  and  then 
simply  ran  overboard,  so  that  the  after  part  of  the  ship 
was  kept  dry. 

Then  troubles  arose  with  the  loading.  The  engines, 
of  course,  need  to  be  in  the  centre,  for  they  represent 
considerable  weight,  which,  if  not  balanced,  will  cause 
one  end  of  the  ship  to  float  too  high  in  the  water. 
Thus  the  hold  of  the  ship  is  divided  by  the  engine- 
room  into  two  approximately  equal  parts,  but  out  of 
the  after-hold  must  be  taken  the  space  occupied  by  the 
tunnel  through  which  the  propeller  shaft  runs,  from 
the  engine  to  the  screw.  Thus  the  capacity  of  the 
after-hold  becomes  less  than  the  forward  one,  and  if 
both  be  filled  with  a  homogeneous  cargo  such  as  grain, 
(and,  as  we  shall  see  presently,  such  a  cargo  must 
always  entirely  fill  the  hold),  the  forward  part  of  the 
ship  would  float  low  in  the  water.  The  trouble  could 
not  be  rectified  by  placing  the  engines  further  forward, 
for  then  the  ship  would  not  float  properly  when 
light. 

Shipbuilders  overcame  this  trouble,  however,  by 
raising  the  whole  of  the  "  quarter-deck  " — the  part  of  the 
deck,  that  is,  which  lies  behind  the  after  end  of  the 
"  bridge-house  " — and  by  that  means  they  made  the  after 
hold  deeper  than  the  other.  Thus  the  commonest 
type  of  all,  the  "  raised  quarter-deck,  well-decker," 
came  into  existence,  a  type  of  which  many  examples 
are  to  be  seen  on  the  sea. 

At  this  point  it  will  be  convenient  to  explain  the 
meaning  of  the  word  "  tonnage  "  as  applied  to  merchant 

139 


Iron  and  Steel  Ships 

vessels.  Originally  it  meant  the  number  of  "tuns" 
of  wine  which  a  ship  could  carry.  Nowadays  it  is 
arrived  at  by  means  of  a  complicated  system  of  measure- 
ments, which  may  be  briefly  explained  thus.  The 
number  of  cubic  feet  in  all  the  enclosed  space  in  the 
hull  and  deck  structures  is  first  ascertained.  That, 
divided  by  100,  gives  the  gross  tonnage.  The  net 
tonnage  is  reckoned  by  deducting  from  the  gross 
tonnage  the  space  occupied  by  engines  and  boilers, 
coal,  water  ballast,  the  accommodation  for  the  officers 
and  crew,  and  other  spaces  entirely  necessitated  by  the 
working  of  the  ship  and  of  no  use  for  stowing  cargo. 
"  Displacement  tonnage "  is  the  weight  of  the  water 
displaced  when  the  ship  is  loaded,  which  is  exactly 
equal  to  the  weight  of  the  ship  and  cargo.  This  last 
system  is  that  employed  for  all  naval  vessels,  so  that 
when  we  are  told  that  the  Dreadnought's  tonnage  is 
17,900  we  know  that  the  hull,  guns,  armour,  and  all 
the  normal  requisites  of  the  ship  actually  weigh  17,900 
tons.  On  the  other  hand  the  gross  tonnage  of  the 
"Orient"  liner  Otranto  is  12,124,  yet  it  displaces 
35,250  tons. 

The  rules  for  determining  gross  and  net  tonnage 
are  somewhat  arbitrary,  and  the  two  tonnages  do  not 
by  any  means  always  bear  the  same  relation  to  each 
other  or  to  the  "  displacement."  The  gross  tonnage 
is  generally  considerably  less  than  the  "  displacement." 

Now  it  is  on  the  net  tonnage  that  the  "  dues  "  are 
paid,  and  so  we  can  now  see  clearly  the  dilemma, 
referred  to  just  now,  which  faces  the  designer  of  a  ship. 
For  considerations  of  seaworthiness  it  is  desirable  to 
have  the  deck  well  above  the  water  line,  in  order  that 
it  may  be  too  high  for  heavy  seas  to  come  on  board. 
That,  however,  will  increase  the  enclosed  space,  and 
consequently  the  net  tonnage,  and  unless  the  cargo 
be  very  light,  to  fill  these  spaces  would  be  to  overload 

140 


Iron  and  Steel  Ships 

the  ship.  Consequently  on  most  voyages  they  would 
have  to  be  empty,  and,  naturally,  the  owner  objects 
to  pay  dues  on  empty  spaces  which  cannot  earn  any 
« freight." 

This  has  led  in  quite  recent  years  to  the  invention 
of  what  are  called  "turret-ships,"1  in  which  the  high 
deck  is  provided,  without  unduly  increasing  the  tonnage. 
In  this  type  the  vertical  sides  come  up  to  some  distance 
above  the  load  line  ;  then  they  curve  in  horizontally, 
and  form  a  narrow  deck  called  the  "  harbour  deck," 


Turret  fac/Ti 


fH 

1 

Turret 

/ 

<_  m 

\                    / 

\    j 

Harbour 

Deck 


Double 

FIG.  24. — Cross  section  of  a  Turret-ship. 

on  each  side  of  the  ship.  From  this  they  curve  up- 
wards to  the  turret  deck.  This  deck,  and  the  two 
short  sides  leading  up  to  it,  thus  form  a  long,  level 
platform  with  parallel  sides,  running  the  whole  length 
of  the  ship,  and  this  platform  is  known  as  "  the  turret." 
(A  part  of  a  turret-ship  can  be  seen  facing  page  182.) 

In  addition  to  the  advantage  of  the  high  deck  with- 
out useless  space,  this  arrangement  makes  a  very  strong 
form  of  structure,  and  so  ships  of  this  type  can  be 
made  comparatively  light.  It  has  a  special  advantage, 

1  These  must  not  be  confused  with  an  old  type  or  naval  vessels  called  by 
the  same  name. 


Iron  and  Steel  Ships 

too,  when  the  cargo  consists  of  material  like  coal  or 
grain. 

Many  ships  have  been  lost  through  a  cargo  of  that 
description  shifting  to  one  side  during  a  gale,  a  danger 
which  can  be  provided  against  by  entirely  filling  the 
hold.  But  a  difficulty  arises  through  the  tendency  of 
the  cargo  to  shake  together ;  so  that,  even  if  the  hold 
be  filled  to  start  with,  it  may  not  remain  full  ;  so 
"  trunks  "  or  deep  shafts  are  constructed,  leading  from 
above  the  deck  down  into  the  hold,  and  these,  being 
filled  right  up,  hold  a  reserve  which  tends  to  fall  down 
into  the  hold  and  keep  it  full.  Of  course,  the  stuff  in 
the  trunks  is  then  liable  to  shift,  but  they  do  not  con- 
tain sufficient  for  that  to  be  of  any  serious  consequence. 

Now  the  turret  of  a  [turret-ship  answers  the  purpose 
of  a  "  trunk "  admirably,  and  the  curved  form  of  the 
hold,  too,  causes  the  cargo  to  settle  down  very  readily. 

The  "harbour  deck"  can  be  utilised  for  loading  long 
things  such  as  timber,  rails,  or  iron  girders. 

Many  ships  of  this  type  have  been  built,  notably 
some  very  fine  vessels  for  the  t(  Clan  "  line. 

In  some  trades,  there  is  only  cargo  to  be  carried  in 
one  direction,  vessels  having  to  return  in  ballast,  and 
for  this  purpose  the  double  bottom  which  all  modern 
steamers  possess,  and  which  will  be  described  presently, 
is  flooded  with  water  to  form  the  ballast.  For  a  rough 
ocean  voyage,  however,  that  is  not  enough,  as  it  does 
not  sink  the  vessel  sufficiently  to  keep  the  screw  always 
immersed.  As  the  stern  of  the  vessel  passes  through  a 
trough  between  two  waves,  the  propeller  may  for  a 
moment  be  out  of  the  water  altogether,  and  then  the 
engine,  having  little  or  nothing  to  resist  it,  begins  to 
"  race  "  ;  it  spins  the  screw  round  very  fast,  with  the 
result  that  a  moment  later,  when  it  strikes  the  water 
again,  the  shock  may  be  sufficient  to  break  something, 
perhaps  the  propeller  shaft  itself. 

142 


Iron  and  Steel  Ships 

More  ballast  space  must,  therefore,  be  provided  for 
ships  engaged  in  these  trades,  and  it  must  not  be  too 
low  down,  or  the  ship  will  roll  badly  from  side  to  side. 
In  some  the  sides  are  made  double,  like  the  bottoms, 
and  rilled  with  water.  In  others  the  boat  is  made 
something  like  a  turret-ship,  only  the  sides  are  carried 
straight  up,  and  the  space  above  what  would  in  a 
turret-ship  be  the  "  harbour  deck "  forms  tanks  for 
water  ballast.  These  are  called  "  cantilever-framed " 
steamers. 

The  majority  of  these   cargo   steamers — in  fact,  all 


Spa  ce  for 
Water 


o  o    o  o 


ooo 


^- Space  For 
Hbter  Bat/tot 


FIG.  25.  —  Cross  section  of  Cantilever-  framed  Steamer. 

those  intended  to  carry  bulk  cargoes  —  have  only  one 
deck,  but  there  are  many  which  have  two  or  more,  so 
that  they  can  more  conveniently  take  a  miscellaneous 
cargo  of  cases  and  packages. 

To  the  landsman,  the  word  "  deck  "  usually  means  the 
main  covering  of  the  ship,  which  runs  from  end  to  end 
about  on  a  level  with  the  bulwarks.  Technically, 
however,  the  word  "  deck  "  is  applied  to  any  floor  in  a 
vessel. 

There  are  many  ships  afloat  known  by  the  name  of 
"  tank  steamers,"  specially  built  for  carrying  oil  in 
bulk.  Originally  these  were  simply  ordinary  ships 
with  tanks  placed  inside  them,  but  they  are  now  built 

143 


Iron  and  Steel  Ships 

so  that  the  vessel  itself  forms  a  series  of  tanks.  There 
is  usually  a  division  called  a  "  bulkhead/'  right  down  the 
middle  of  the  ship,  and  transverse  bulkheads  at  frequent 
intervals,  and  these  with  the  sides  of  the  ship  constitute 
"oil-tight"  reservoirs  in  which  the  oil  can  be  carried. 
There  are  always  two  decks,  the  lower  of  which  forms 
the  top  of  the  tanks,  while  between  the  two  are 
trunks  for  the  purpose  of  ensuring  that  the  tanks  shall 
always  be  quite  full,  an  arrangement  similar  to  that 
described  for  steamers  carrying  grain.  Suitable  pipes 
are  provided  by  which  the  oil  can  be  pumped  out,  and 
in  this  way  a  ship  carrying  1700  tons  of  oil  can  be 
discharged  in  about  six  hours.  Air  pumps,  too,  are  in 
many  cases  provided  to  suck  out  the  explosive  vapour 
which  is  left  in  the  tanks  when  they  are  emptied  of  oil, 
and  which,  being  heavier  than  air,  does  not  disperse 
itself. 

Special  care  has  to  be  taken  to  prevent  any  leakage 
of  oil  into  the  boiler-room.  For  this  reason  there  are 
generally  two  bulkheads  between  the  oil  and  the  boilers, 
the  space  between  which  is  either  filled  with  water  or 
provided  with  a  pump  to  remove  quickly  any  oil  that 
may  leak  into  it. 

For  the  same  reason,  the  engines  and  boilers  are 
often  placed  right  aft,  since  then  the  oil  can  only  leak 
towards  the  engine  and  boiler  space  from  one  side,  and 
not  from  two  sides,  as  must  be  the  case  if  the  engines 
are  in  the  middle.  When  light,  such  a  steamer,  of 
course,  floats  with  its  stern  low  in  the  water,  or  "  trims 
by  the  stern,"  to  use  the  nautical  phrase,  but  that  is 
quite  as  it  should  be,  for  it  ensures  that  the  propeller 
shall  be  sufficiently  immersed,  and  the  bow  being  high 
is  of  no  consequence. 

Some  of  these  steamers  are  very  large  ;  there  is  at 
least  one  with  a  displacement  of  2 1,000  tons — more  than 
that  of  the  Dreadnought. 

144 


Iron  and  Steel  Ships 

In  vessels  which  carry  passengers  as  well  as  cargo 
the  conditions  are  somewhat  different  from  those  which 
apply  to  cargo  vessels.  They  are,  generally  speaking, 
larger,  and  the  difficulties  with  regard  to  the  high  deck 
do  not  apply,  for  the  space  which  would  be  wasted  on 
a  purely  cargo  boat  can  be  used  for  the  passenger 
accommodation.  They  are  therefore  built  with  a  larger 
"  freeboard,"  by  which  is  meant  the  distance  from  the 
water-line  to  the  gunwale.  There  are  generally  several 


Boat-  Deck 


Stipei 


Hull 

Proper  { 


Upper  Promenade  Dk. 


Promenade  DK. 


Lower  Promenade  Dk. 


VpperDK. 


MainDK. 


Lower  DK. 


Orlop  DK. 


Wafe 


o  fo    ooo 


FIG.  26. — Section  of  modern  liner,  showing  the  decks. 

decks  forming  part  of  the  actual  hull  of  the  ship,  and 
several  more  which  are  really  the  floors  of  a  building 
of  lighter  construction  than  the  hull,  and  not,  strictly 
speaking,  a  part  of  the  ship,  but  simply  erected 
upon  it. 

As  an  example  of  a  large  passenger  and  cargo 
steamer,  a  section  is  given  in  Fig.  26  of  the  latest 
transatlantic  liner,  the  George  Washington.  This  boat 
has  not  been  designed  to  break  speed  records, 
but  simply  to  give  passengers  a  comfortable  and 

145  K 


Iron  and  Steel   Ships 

reasonably  quick  voyage,  and  also  to  carry  a  fair 
amount  of  cargo. 

It  will  be  seen  that  there  are  eight  decks,  the  lowest 
six  of  which  are  actually  a  part  of  the  ship,  while  the 
two  top  ones  are  part  of  the  superstructure. 

The  "lower  deck"  is  just  level  with  the  water-line, 
so  that  it  and  all  those  above  it  are  available  for  accom- 
modating the  passengers  and  crew,  while  the  one  under- 
neath and  the  space  below  it  are  available  for  cargo, 
stores,  and  machinery. 

Passenger  steamers  are  invariably  divided  up  into 
water-tight  compartments.  At  frequent  intervals  there 
are  complete  transverse  bulkheads  or  water-tight 
dividing  walls,  with  water-tight  doors  in  them.  These 
doors  are,  in  some  cases,  arranged  so  that  they  can  be 
closed  from  the  bridge  either  by  hydraulic  power  or 
electricity.  In  some  ships  a  more  safe  arrangement 
still  obtains,  there  being  no  opening  at  all  in  the 
bulkheads,  so  that,  to  get  from  one  compartment  to 
another,  a  man  has  to  go  up  to  one  of  the  upper  decks, 
above  the  water-line.  A  ship  fitted  like  this  has  little  to 
fear  from  a  collision,  for  one  or  two  compartments 
may  be  filled  with  water  without  any  risk  of  her 
sinking. 

The  fitting  and  furnishing  of  high-class  passenger 
steamers  is  of  the  most  elaborate  description,  but  as  so 
much  has  been  written  about  that  in  the  daily  press  and 
magazines,  and  as,  moreover,  it  is  more  in  the  province 
of  the  architect  than  the  engineer,  it  is  not  necessary  to 
go  into  details  here. 


146 


CHAPTER   XI 
THE  BUILDING  OF  SHIPS 

THE  last  chapter  deals  mainly  with  the  general  features 
of  various  types  of  merchant  vessels.  We  now  come 
to  the  method  by  which  ships  are  designed  and  built. 

It  must  be  understood  that  a  ship  floats  as  the  result 
of  the  balancing  of  two  opposing  forces.  Gravity  tends 
to  pull  the  ship  downwards,  but  that  is  resisted  by  an 
upward  force  due  to  the  displacement  of  a  certain 
quantity  of  water  by  the  ship.  When  a  vessel  is 
launched,  it  sinks  until  it  has  displaced  or  pushed  aside 
a  volume  of  water  exactly  equal  in  weight  to  its  own 
weight.  Then  the  two  forces  exactly  balance  and  it 
neither  sinks  nor  rises.  As  it  is  loaded  it  sinks  farther, 
displacing  a  further  weight  of  water  equal  to  the  weight 
of  the  cargo.  If  a  vessel  be  loaded  until  its  weight 
exceeds  the  weight  of  water  which  it  is  able  to  displace 
it  sinks  ;  that  is  what  so  often  happens  when  water 
rushes  in  after  a  collision. 

But  it  is  not  sufficient  for  a  ship  merely  to  float. 
It  must  maintain  an  upright  position.  This  is  ensured 
by  giving  it  such  a  shape  that  the  centre  of  gravity  and 
the  centre  of  buoyancy  will  naturally  place  themselves 
in  a  vertical  line. 

The  meaning  of  the  "  centre  of  gravity "  is  pretty 
generally  understood,  but  the  other  term  may  need 
a  little  explanation.  It  means  the  centre  of  gravity  of 
the  water  which  the  ship  displaces.  Thus,  one  is  the 
point  about  which  all  the  downward  forces  balance, 


The   Building  of  Ships 

while  the  other  is  the  point  about  which  the  upward 
forces  balance. 

In  Fig.  27  we  see  the  ft  midship  "  section  of  a  ship  in 
its  upright  position,  and  it  will  be  seen  that  the  two 
" centres"  are  exactly  in  a  line  vertically.  In  Fig.  28 


FIG.  27.  FIG.  28. 

Midship  section  of  a  ship  showing  why  it  floats  upright.  Normally 
the  centre  of  gravity  and  the  centre  of  buoyancy  are  in  the  same  vertical 
line.  If  the  ship  inclines  to  one  side,  the  centre  of  buoyancy  moves  to 
that  side  too  and  tends  to  push  it  back  to  the  upright  position. 

the  same  ship  is  shown  when  leaning  over  to  one  side. 
Now  it  is  easy  to  see  that  the  shape  of  the  displaced 
water  (shown  shaded  in  both  figures)  is  different  in 
these  circumstances  from  what  it  is  when  the  ship  is 
upright,  and  this  difference  in  shape  shifts  the  centre  of 


FIG.  29.  FIG.  30. 

A  ship  of  this  shape  would  be  unstable,  for  the  centre  of  buoyancy 
would  remain  under  the  centre  of  gravity  (or  rather  would  move  slightly 
in  the  opposite  direction  to  the  inclination  of  the  ship),  and  so  there  would 
be  no  tendency  to  "  right"  itself. 

buoyancy  to  the  right.  It  is  easy  to  see,  too,  that  the  up- 
ward force  of  buoyancy  and  downward  force  of  gravity, 
acting  together,  will  then  tend  to  "right"  the  ship. 

By  way  of  contrast  Figs.  29  and  30  show  a  form  of 
vessel  which  will  tend,  not  to  keep  upright,  but  to  turn 
over. 

148 


The  Building  of  Ships 

We  may  say,  then,  that  the  stability  of  a  ship  depends 
upon  its  shape. 

One  thing  the  designer  has  to  do,  then,  is  to  give  his 
vessel  such  a  size  and  form  that  it  will  sink  to  the 
required  depth  under  the  required  load,  and  that  it  will 
float  in  an  upright  position.  In  this,  however,  as  in 
many  other  matters,  he  has  to  use  a  nice  discrimination  ; 
for,  if  he  makes  his  centre  of  gravity  too  low,  the  ship 
will  be  very  safe  from  the  risk  of  capsizing  but  it  will 
roll  terribly.  ]  udgment,  experience,  and  wide  knowledge 
are  all  necessary,  therefore,  for  the  designing  of  a  ship. 

Most  of  us  at  some  time  or  other,  probably  on  a 
summer  evening,  have  watched  a  ship  riding  at  anchor 
on  a  smooth  sea,  like  the  Ancient  Mariner's  craft — 

"  As  idle  as  a  painted  ship 
Upon  a  painted  ocean," 

and  it  has  seemed  the  perfect  embodiment  of  peace  and 
rest.  Yet  there  were  forces  within  and  around  that  ship 
endeavouring  to  distort  it  and  rend  it  asunder.  The 
only  reason  why  they  were  not  apparent  was  because 
the  ship  was  strong  enough  to  resist  them.  And  the 
reason  why  it  was  strong  enough  ?  The  designer  had 
analysed  and  calculated  those  forces  and  provided 
against  them. 

Suppose  we  were  to  make  a  model  boat  of  some 
flexible  substance,  such  as  indiarubber,  and  fill  it  with 
alternate  pieces  of  lead  and  cork. 

It  would  float  something  like  the  sketch  (Fig.  31), 
bent  and  distorted  by  the  varying  degrees  of  buoyancy 
of  its  different  parts,  and  the  different  weights  of  the 
lead  and  cork.  If,  however,  our  model  were  made  of 
stiff  material  like  iron,  it  would  retain  its  shape  as  in 

Fig-  32. 

In  precisely  the  same  way  some  parts  of  a  ship  are 
more  buoyant  than  others,  and  some  are  more  heavily 

149 


The  Building  of  Ships 

loaded  than  others,  and  the  heaviest  loads  do  not  always 
come  where  the  greatest  buoyancy  is,  so  that  if  a  ship 
were  not  made  stiff  enough  it  would  be  distorted  like 
the  indiarubber  model.  By  very  laborious  methods,  all 
these  stresses  have  to  be  calculated  out  and  the  ship 
made  stiff  enough  to  resist  them.  The  pressure  of  the 


FIG.  31.  —  This  is  how  a  ship  would  be  distorted  by  the  various 
loads  within  it,  were  it  not  rigid  enough. 

water,  too,  is  always  trying  to  push  the  sides  of  the 
vessel  together,  and  the  ends  inwards  towards  the 
middle. 

All  these  forces  are  at  work  constantly,  even  in  still 
water.  What  must  the  condition  be,  then,  in  a  storm  ? 
The  worst  stresses  of  all  that  a  ship  has  to  withstand  are 


r_j  -  jj 

'     i  i  i    i 


FIG.  32. — This  is  how  the  same  boat  floats  when  it  is  rigid.  The  comparison 
of  these  two  show  us  how  a  ship  is  being  strained  by  powerful  forces  even 
when  lying  at  anchor  in  still  water. 

those  caused  by  crossing  large  waves  at  a  distance  apart 
equal  to  its  own  length.  It  is  then  (see  Fig.  33)  lifted 
by  the  water  at  both  ends,  and  almost  unsupported  in 
the  middle,  while  at  other  times  (see  Fig.  34),  it  is  lifted 
in  the  middle  but  not  at  the  ends.  Under  these  condi- 
tions its  position  much  resembles  that  of  a  bridge. 
Indeed,  there  is  much  in  common  between  a  bridge 


The  Building  of  Ships 

and  a  ship,  and  it  may  almost  be  said  that  the  modern 
steel  ship  is  the  lineal  descendant  of  a  certain  railway 
bridge.  It  came  about  in  this  way.  Failure  though  it 
was,  the  famous  Great  Eastern  has  undoubtedly  had 
a  great  influence  on  the  design  of  modern  steel  ships, 
and  it  was  the  embodiment  of  very  original  ideas.  These 
its  designer,  the  famous  engineer,  I.  K.  Brunei,  drew 


FIG.  33. — This  shows  how  two  waves  lift  a  ship  at  the  ends. 

very  largely  from  the  famous  tubular  bridge  which  his 
friend  Robert  Stephenson  constructed  over  the  Menai 
Straits  in  Wales. 

In  a  previous  chapter  on  bridges  the  ordinary  "  plate 
girder "  has  been  described,  consisting  of  a  vertical 
"  web  "  connecting  two  horizontal  "  flanges."  Some- 
times such  a  girder  is  made  with  two  webs  instead  of 


FIG.  34. — This  shows  how  a  wave  lifts  a  ship  in  the  middle. 

one,  a  little  distance  apart,  and  it  then  is  called  a  "  box 
girder."  Its  principle  is  exactly  the  same  as  the  single- 
web  girder,  the  difference  being  simply  one  of  con- 
struction. 

Now  a  modern  steel  ship  owes  its  ability  to  resist  the 
worst  of  the  forces  which  assail  it  to  the  fact  that  it  is 
a  box-girder.  The  bottom  is  the  lower  flange,  the 
decks  are  the  upper  flange,  while  the  sides  are  the  webs. 

In  designing  a  ship,  then,  the  designer  first  of  all 
settles  the  size — the  length,  breadth,  depth,  and  draught. 


The   Building  of  Ships 

Then  he  settles  the  "  midship  section,"  and  from  it  de- 
velops the  general  form  of  the  vessel,  shaping  it  so  as 
to  have  the  necessary  stability,  to  slip  through  the  water 
easily,  to  have  the  necessary  buoyancy,  to  be  easily 
steerable,  and  numerous  other  conditions,  many  of  which 
only  an  instinct  born  of  experience  and  study  can 
teach  him.  Then  the  details  of  the  design  have  to  be 
worked  out,  due  regard  being  had  to  the  various  forces 
which  we  have  already  noticed  as  being  exercised  upon 
the  ship  by  its  load  and  the  water,  with  other  minor 
forces  too  numerous  to  mention  here.  As  one  who  has 
had  some  experience  in  the  comparatively  simple  art 
of  bridge  design,  the  writer  does  not  hesitate  to  describe 
the  designing  of  a  large  ship — to  meet  all  the  various 
demands  of  speed,  comfort,  safety,  strength,  and  carry- 
ing capacity — as  the  most  difficult  feat  in  the  whole 
realm  of  engineering  practice. 

When  the  design  has  been  completely  worked  out 
on  paper,  and  probably  embodied  in  a  model  as  well, 
it  is  sent  to  the  mould  loft.  This  is  a  capacious  build- 
ing sometimes  half  as  Ipng  as  the  proposed  ship,  and 
its  wooden  floor  constitutes  a  huge  drawing-board. 
On  this  the  details  of  the  ship  are  "set  out"  in  chalk 
full  size.  Then  upon  another  large  but  portable 
drawing-board  the  exact  shape  of  each  successive  pair 
of  ribs  is  drawn.  To  ensure  permanency  the  lines  are 
cut  into  the  wood  with  a  sharp  tool,  and  then  the 
portable  board  is  taken  to  the  workshops  where  the 
drawings  are  reproduced  in  steel. 

A  ship  is  built  from  the  keel  upwards.  First  of  all 
piles  of  timbers  are  placed  in  a  row  on  slightly  sloping 
ground  near  the  water's  edge.  These  piles  of  timbers 
are  known  as  the  "keel  blocks."  Upon  them  is  built 
up  a  huge  plate  girder,  in  a  large  ship  as  much  as 
five  feet  in  depth.  The  bottom  flange  of  this  girder 
forms,  strictly  speaking,  the  keel,  and  the  girder  itself 

152 


The  Building  of  Ships 

fulfils  a  function  precisely  analogous  to  that  of  the 
backbone  of  an  animal. 

To  the  central  girder  are  riveted,  on  each  side, 
other  girders  which  form  the  ribs.  These  are  nearly 
as  deep  as  the  central  girder  at  one  end,  but  they  taper 
off,  and  at  the  same  time  curve  upwards,  according  to 
the  shape  of  the  bottom  of  the  vessel.  A  reference  to 
Fig.  35  will  make  this  quite  clear. 

At  intervals  between  these  ribs,  and  at  right  angles 
to  them,  other  girders  are  fitted,  so  that  the  whole 


OufierStin 


FIG.  35.— Section  showing  the  double  bottom  of  a  modern  ship.  B  is  the 
central  girder  or  backbone,  the  bottom  flange  of  which  (K)  forms  the  keel. 
The  ribs  (R)  are  fixed  in  pairs,  one  each  side  of  the  backbone,  and  be- 
tween them  the  longitudinals  (L)  are  fitted.  Both  upper  and  under  sides 
are  covered  with  plating,  and  at  the  ends  the  side  frames  (S  F)  are 
erected ;  they  are  plated  on  the  outside  only.  The  holes  (H)  in  the 
ribs  are  put  in  for  the  sake  of  lightness. 

form  an  enormously  strong  framework,  which  is  then 
covered  with  a  "  skin "  of  steel  plates  both  above 
and  below.  Thus  the  hollow  "  double-bottom  "  of  the 
ship  is  formed.  This  form  of  structure,  which  is  one 
of  those  features  derived  indirectly  from  the  Menai 
Bridge,  is  not  only  of  the  greatest  possible  strength, 
but  it  provides  a  space  between  the  two  skins  which 
can  be  filled  with  water  for  ballasting  the  ship  ;  more- 
over, should  the  vessel  run  aground  and  perforate 
the  outer  skin,  the  inner  one  will  prevent  her  from 
sinking. 

Then,   all  around  the  edge  of  this  double    bottom 

153 


The  Building  of  Ships 

strong  vertical  girders  are  erected,  which  form  the 
"  side-frames,"  and  horizontal  girders  fitted  between 
these  make  up  a  structure  similar  to  that  of  the  bottom, 
except  that  on  the  sides  there  is  an  outer  "  skin  "  only. 

All  the  connections  are  made  with  rivets  which 
are  put  in,  as  far  as  possible,  with  the  "  iron  man  " 
described  in  an  earlier  chapter,  since  the  enormous 
pressure  exerted  by  the  "  pinching "  action  of  this 
machine  ensures  that  the  rivet  shall  entirely  fill  the 
hole  and  make  a  very  tight  joint.  Where  an  iron 
man  cannot  get  at  them,  the  rivets  are  closed  by  hand 
or  with  a  pneumatic  "  pistol  "  riveter,  also  described 
in  the  chapter  on  tools. 

The  joints  in  the  plates  are  made  water-tight  by 
caulking.  This  process  consists  in  hammering  the 
edge  of  the  uppermost  plate  with  a  tool  like  a  blunt 
chisel,  thereby  swelling  it  out  and  causing  it  to  press 
tightly  against  the  other  plate,  and  closing  up  any  gap 
there  may  be  between  the  two. 

The  side  frames  are  connected  across  the  ship  by 
beams  which  support  the  deck,  and  these  again  are 
covered  with  steel  plates,  completing  the  structure, 
and  forming,  as  was  remarked  just  now,  a  huge  box 
girder. 

The  transverse  strength  is  still  further  increased,  as 
well  as  the  safety  of  the  ship  made  more  secure,  by  the 
cross  partitions  or  bulkheads  which  are  placed  right 
across  the  ship  at  intervals. 

The  stem  and  the  stern  of  a  large  ship  are  each 
formed  of  a  huge  steel  casting. 

It  will  be  noticed  in  the  above  description  that, 
except  for  the  "  central  girder "  or  backbone,  all 
the  main  members  of  the  structure  are  transverse 
with  short  longitudinal  members  fitted  between  them. 
That  is  usual  in  merchant  ships,  but  in  the  Navy  the 
opposite  plan  is  the  practice.  In  war-vessels,  the 

154 


CHAPTER   XII 

CURIOUS   SHIPS 

SHIPS  are  always  interesting,  but  there  are  some  which 
are  especially  so  because  of  their  unusual  form  or 
strange  purpose.  In  this  chapter  I  am  going  to 
describe  some  of  these  special  craft. 

The  great  navies  do  not  consist  entirely,  as  we 
might  think,  of  fighting  ships.  Just  as  the  old  knights 
of  the  Middle  Ages  used  to  be  accompanied  on  their 
campaigns  by  armourers  who  could  repair  any 
damage  to  their  masters'  weapons,  so  the  fleets  of 
the  modern  navies  are  sometimes  accompanied  on 
their  voyages  by  repair-ships — floating  factories — on 
which  quite  large  repairs  can  be  effected  at  sea. 

The  most  recent  of  these  in  the  British  Navy  is  the 
Cyclops,  and  it  is  so  wonderfully  fitted  up  that  it  is  well 
worth  description. 

To  look  at,  it  is  much  like  an  ordinary,  fair-sized 
cargo  steamer ;  indeed  it  was  being  built  as  such, 
and  was  half-finished  when  purchased  by  the  British 
Admiralty  and  adapted  to  its  present  purpose. 

It  has  on  board  an  iron-foundry  in  which  iron 
castings  up  to  a  ton  in  weight  can  be  made,  also 
brass  castings  ;  a  smithy  with  an  equipment  of  tools 
and  appliances  which  many  a  works  ashore  would 
envy.  There  are  huge  stores  of  iron  and  steel  of 
all  sorts,  shapes,  and  sizes,  with  timber  to  supply  the 
capacious  carpenter's  shop. 

There  are  "  machine  shops "  fitted  with  lathes  and 


Curious  Ships 

other  machine-tools,  and  a  boiler-shop  capable  of 
turning  out  quite  large  work. 

Indeed  it  may  be  regarded  as  a  well-equipped  and 
up-to-date  engineering  works,  on  four  floors.  Four 
electric  lifts  carry  goods  and  passengers  from  one 
floor  or  deck  to  another.  The  power  is  generated  in  a 
"  central  station  "  and  conveyed  electrically  to  various 
parts  of  the  ship,  where  seventeen  electric  motors  drive 
machines  or  groups  of  machines.  Several  of  the  larger 
"shops"  are  lit  by  large  "arc"  lamps,  just  as  large 
workshops  ashore  often  are. 

There  is  a  distilling  apparatus  for  making  pure  water, 
an  ice-machine,  a  bakery  with  a  motor-driven  dough- 
mixer,  and  of  course  wireless  telegraphy. 

The  ship  itself  is  propelled  by  twin-screws,  and  can 
steam  at  fourteen  knots  per  hour. 

Complete  assortments  of  portable  tools  are  carried, 
so  that  the  Cyclops  men  can  sally  forth  to  execute 
repairs  in  situ  upon  the  other  ships,  while  there  are 
powerful  winches,  derricks,  and  cranes  upon  the  deck, 
by  which  heavy  pieces  can  be  lifted  from  other  vessels 
for  treatment  on  board. 

We  are  all  familiar  with  the  methods  by  which  coal 
is  unloaded  from  ships.  Sometimes  it  is  shovelled  into 
baskets,  which  are  pulled  up  by  hand  and  then  tipped 
over  the  side — a  very  primitive  method.  A  more 
modern  way  is  to  have  large  steel  buckets  which 
are  filled  by  men  in  the  hold,  and  which  are  then 
drawn  up  by  a  steam-crane.  Still  more  refined  is 
the  use  of  a  "  grab,"  a  huge  "  hand  "  which  is  let  down 
on  to  the  coal  by  a  crane,  and  which,  on  being  pulled, 
grasps  a  "  handful "  which  it  holds  until  released  by 
some  suitable  means,  when  it  opens  and  lets  the  coal 
fall. 

The  best  of  these  methods,  however,  is  thrown  into 

164 


Curious  Ships 

the  shade  by  a  "  self-discharging "  collier  which  has 
recently  been  built.  It  can  carry  3100  tons  of  coal, 
and  can  discharge  all  of  it  in  about  eight  hours,  at  a 
cost  of  about  one-tenth  that  of  any  other  method. 

At  the  bottom  of  the  ship  is  what  might  be  called  a 
"  false  bottom/'  forming  a  clear  space  underneath  the 
cargo  the  whole  length  of  the  ship.  In  this  space  there 
are  "belt  conveyers."  Doors  can  be  opened  to  allow 
the  coal  to  fall  upon  these  conveyers,  and  it  is  carried 
by  them  to  one  end  of  the  ship,  where  they  deliver  it 
to  other  conveyers  which  take  it  up  to  the  level  of  the 
deck.  Here  there  are  other  conveyers,  each  enclosed 
in  a  large  pipe  which  can  be  swivelled  round  and  raised 
or  lowered  at  will. 

To  unload  the  vessel,  these  pipes  are  placed  in 
position,  with  their  ends  over  the  barge,  railway  truck, 
or  whatever  it  may  be  that  the  coal  has  to  be  discharged 
into,  the  conveyers  are  set  going,  and  some  of  the 
doors  opened.  Quite  automatically,  then,  the  coal 
commences  to  travel  to  the  after-end  of  the  ship,  then 
up  to  the  deck  and  through  the  pipes,  from  the  end  of 
which  it  falls,  like  water  from  the  spout  of  a 'tea-kettle. 

The  <{  false  "  floor  slopes  towards  the  conveyers,  so 
that  quite  75  per  cent,  of  the  cargo  discharges  itself, 
the  remainder  having  to  be  assisted  by  a  little  hand 
labour. 

An  automatic  weigher  is  fitted,  which  silently  records 
the  quantity  of  coal  which  passes. 

There  are  some  very  interesting  boats  used  for 
dredging,  a  very  important  operation  in  connection 
with  all  seaports. 

A  fine  example  of  this  kind  of  craft  has  recently  been 
built  for  use  at  Venice.  It  is  a  twin-screw  steamer, 
capable  of  going  a  sea-voyage  under  its  own  steam,  and 
it  can  dredge  in  two  ways. 

165 


Curious  Ships 

One  is  by  means  of  buckets  or  scoops  fixed  to  a 
chain.  In  the  centre  of  the  vessel  there  is  a  large 
opening,  down  which  a  "  ladder/*  as  it  is  called,  can  be 
lowered.  This  is  a  powerful  steel  girder,  one  end  of 
which  is  pivoted  on  the  ship,  while  the  other  can  be 
lowered  down  on  to  the  bed  of  the  channel  to  be  dredged, 
and  at  each  end  of  it  there  is  a  roller.  Around  these 
two  rollers  there  is  an  endless  chain,  built  up  of  steel 
links  and  pins,  something  after  the  manner  of  a  cycle- 
chain,  and  to  this  chain  the  buckets  are  fixed.  In 
operation,  the  free  end  of  the  ladder  is  let  down  and 
the  upper  of  the  two  rollers  is  turned  round  by  the 
engine.  This  causes  the  chain  to  move ;  the  buckets 
are  carried  down  the  under  side  of  the  ladder  and  scrape 
along  the  bottom,  each  scooping  up  its  load  of  mud  and 
returning,  filled,  along  the  upper  side  of  the  ladder. 
On  reaching  the  upper  roller,  each  bucket,  perforce, 
turns  over,  and  in  so  doing  throws  its  contents  into  a 
hopper  on  the  vessel  or  through  shoots  into  barges 
lying  alongside.  This  particular  vessel  can  reach  down 
to  a  depth  of  66  feet,  and  scoop  up  over  500  tons  of 
mud  per  hour. 

Its  second  mode  of  action  is  by  suction.  Under  some 
conditions  it  is  possible  to  suck  the  mud  up  better  than 
to  dig  it  up.  For  this  purpose  a  large  pipe  is  let  down, 
and  a  powerful  pump  on  board  sucks  water  up  it, 
bringing  the  mud  with  it. 

It  is  often  easier  to  dredge  the  mud  up  out  of  a 
channel  than  it  is  to  get  rid  of  it,  for  it  must  be  con- 
veyed to  some  place  where  it  will  not  be  likely  to  be 
carried  back  into  the  channel.  The  common  way  is  to 
deposit  it  in  barges  for  conveyance  to  some  suitable 
spot,  and  that  method  is  provided  for  here  ;  but  there 
are  two  other  ways  as  well.  This  dredger  has  a  hopper 
which  is  capable  of  holding  1000  tons,  so  that  it  can, 
if  desirable,  be  its  own  barge,  and  when  its  hopper  is 

166 


Curious  Ships 


full  it  can  steam  away  and  dump  the  contents  out  at 
sea.  The  hopper  has  a  bottom  formed  of  doors  which 
can  be  let  down,  dropping  the  whole  of  the  contents 
into  the  water  in  a  moment. 

The  last  way  of  disposing  of  the  mud  is  the  most 
interesting  of  all.  Think  of  a  huge  pipe,  with  flexible 
joints,  2000  feet  long,  floating  on  the  surface  of  the 
water,  a  veritable  "  sea-serpent."  Through  such  a 
pipe  the  dredger  can  pump  its  sludge,  discharging  it 
into  the  water  2000  feet  away. 

In  the  harbour  at  Bombay  there  is  a  quantity  of 
low-lying  land,  some  of  which  (about  a  square  mile)  is 
now  being  reclaimed,  in  order  to  provide  a  site  for 
railway  sidings.  This  is  being  done  by  depositing 
material  upon  it,  obtained  from  the  bottom  of  the 
harbour  itself,  and  two  special  dredgers  have  been 
built  for  the  purpose. 

They  work  by  suction,  as  the  Venetian  dredger  does, 
but  there  is  in  this  case  a  rotary  cutter — a  sort  of 
gigantic  auger — fixed  at  the  mouth  of  the  suction- 
pipe.  This  cuts  up  the  material,  some  of  which  is 
heavy  clay,  and  renders  it  capable  of  being  drawn 
through  the  pipe.  So  powerful  is  the  suction  that 
lumps  of  stone  of  400  Ibs.  weight  have  been  sucked  up. 

Having  dug  up  and  raised  the  clay,  the  dredger 
then  drives  it  along  a  line  of  pipes,  4500  feet  long, 
the  end  of  which  is  on  the  land  to  be  raised.  One 
of  these  dredgers  has  delivered  as  much  as  2700 
cubic  yards  an  hour,  and  together  they  are  able  to 
do  in  an  hour  as  much  work  as  5000  carts  and  an 
army  of  men  could  do  in  a  day  by  old  methods. 

Perhaps  a  word  of  explanation  is  not  out  of  place 
here  with  regard  to  the  pumps  employed.  It  is 
easy  to  see  that  an  ordinary  pump  could  not  be 
used  for  suction-dredging,  because  the  lumps  of 


Curious  Ships 


earth  would  prevent  the  valves  closing  properly  ;  so 
this  method  would  be  practically  impossible  but  for 
the  existence  of  the  centrifugal  pump,  which  has 
no  valves. 

Every  one  must  have  observed  that  when  a  liquid  in 
a  round  vessel — tea  in  a  teacup,  for  example — is  stirred 
so  that  is  rotates,  it  shows  a  desire  to  escape  outwards, 
away  from  the  centre.  Being  restrained  from  getting 
away  by  the  strength  of  the  vessel,  it  heaps  itself  up 
round  the  edge,  the  faster  it  is  stirred,  the  higher 
being  the  heap  ;  and  if  an  outlet  were  provided  it 
would  rush  out  with  considerable  energy,  due  entirely 
to  the  centrifugal  force  caused  by  the  rotating  move- 
ment. If,  then,  we  construct  a  strong,  circular,  closed 
vessel,  with  a  wheel  inside  it  having  vanes  or  paddles 
so  that  it  can  impart  a  spinning  motion  to  water, 
with  an  inlet  near  the  centre  and  an  outlet  at  the 
circumference,  we  shall  have  a  powerful  pump.  For 
we  need  only  fill  it  with  water  and  drive  the  wheel 
round  to  cause  the  water  to  fly  out  of  the  outlet,  and 
at  the  same  time  other  water  will  be  sucked  in  through 
the  inlet  to  take  its  place.  That,  then,  is  the  principle 
of  the  centrifugal  pump,  without  which  suction  dredgers 
would  be  impossible. 

A  new  cable-repairing  ship  has  recently  been  launched 
at  Newcastle-on-Tyne,  which  affords  an  excellent  ex- 
ample of  this  interesting  kind  of  vessel.  Her  name  is 
Telconia,  and  she  belongs  to  one  of  the  great  submarine 
cable-repairing  companies. 

Her  capacity  is  1000  tons,  and  she  is  driven  by  twin 
screws  with  triple-expansion  engines.  Externally  she 
is  not  unlike  an  ordinary  merchant  vessel,  except  that 
at  the  bow,  just  where  the  figure-head  used  to  be  in 
old  vessels,  and  at  the  stern,  just  over  the  rudder,  there 
are  two  large  sheaves  or  pulley-wheels  over  which  the 

168 


Curious  Ships 


cable  can  be  hauled  in  or  let  out.  Inside,  however, 
she  is  arranged  quite  differently  from  the  ordinary  ship, 
for  all  the  quarters  for  the  crew  are  at  the  after-end, 
and  the  whole  front  part  of  the  ship  is  given  up  to  the 
special  machinery  and  appliances  which  are  needed  for 
its  special  work.  First  and  foremost,  there  are  two 
picking-up  machines,  steam  winches  of  a  somewhat 
special  form.  Then  there  are  stores  of  grapnels,  ropes, 
buoys,  and  other  special  tools  and  apparatus,  all  arranged 
so  that  they  can  be  got  out  for  use  quickly,  if  required. 
An  electrician's  room,  too,  with  many  special  forms 
of  instruments,  is  an  indispensable  part  of  the  outfit. 
Finally,  there  are  huge  bunks  for  storing  cable. 

The  principal  functions  of  a  ship  of  this  description 
is  to  go  to  a  damaged  cable,  pick  it  up,  repair  it,  and 
then  lay  it  down  again.  The  electricians  at  the  shore 
end  are  able  to  tell  how  far  off  the  fault  is,  and  as  the 
course  of  a  cable  is  always  carefully  recorded  as  it  is 
laid,  the  position  of  the  fault  on  the  ocean  bed  can  be 
determined  very  nearly.  The  ship  then  proceeds  to 
the  spot  and  starts  to  fish  for  the  cable.  She  lowers 
her  grapnel  about  a  mile  to  one  side  of  the  supposed 
position  of  the  cable,  and  then  very  slowly — a  mile  an 
hour  or  even  slower — she  steams  or  drifts  across  it. 

There  are  several  kinds  of  grapnel  used,  according 
to  the  nature  of  the  sea-bottom,  but  the  most  usual  is 
called  the  "  centipede,"  from  its  resemblance  to  the 
active  little  insects  of  that  name.  It  consists  of  a 
central  shank,  with  little  hooks,  like  the  flukes  of 
small  anchors,  projecting  from  it.  Sooner  or  later — 
sometimes  remarkably  soon — this  picks  up  the  cable, 
which  is  then  drawn  up  on  board. 

First  it  is  cut  and  tested  electrically  to  see  in  which 
half  the  fault  lies  and  how  far  away  it  is ;  the  good  end 
is  then  tied  to  a  buoy  and  dropped  overboard,  while 
the  ship  pulls  in  the  other  end,  slowly  steaming  along 

169 


Curious  Ships 


as  it  does  so.  Periodically  the  cable  is  cut  and  tested 
to  see  if  the  fault  has  been  reached,  and  as  soon  as  it 
has  a  new  piece  is  spliced  on.  Then  the  ship  returns, 
paying  out  the  new  cable  as  it  goes,  until  it  reaches  the 
buoy.  The  "  good  "  end  is  by  that  means  recovered, 
spliced  to  the  new  piece,  the  whole  cable  dropped  back 
into  the  sea,  and  the  work  is  finished. 

What  must  surely  be  a  unique  vessel  has  just  been 
built  at  Stockholm,  for  it  deliberately,  and  of  set  pur- 
pose, capsizes  itself. 

The  city  of  Stockholm  is  built  upon  rock,  which  has 
frequently  to  be  blasted  away  for  any  such  works  as 
road  extensions  or  harbour  improvements,  and  the  only 
way  of  disposing  of  it  is  to  take  it  out  and  drop  it  in 
the  sea.  That  is  the  purpose  of  this  boat. 

It  is  really  a  barge  with  a  perfectly  flat  deck,  but 
with  a  low  bulwark  on  three  sides.  On  this  deck  the 
stone  is  heaped,  and  the  barge  is  then  towed  out  to  sea. 

Now  on  the  side  which  has  no  bulwark,  there  is  a 
cylindrical  steel  tank,  supported  fifteen  feet  or  so  above 
the  deck,  on  tall  columns,  while  on  the  opposite  side, 
under  the  deck,  there  is  another  similar  cylinder  with 
a  third  smaller  cylinder  beside  it.  Ordinarily  the  high 
cylinder  is  empty,  the  low  cylinder  is  full  of  water,  and 
the  small  one  full  of  compressed  air,  things  being  so 
arranged  that  the  tank  full  of  water  just  balances  the 
elevated  tank  when  the  latter  is  empty,  so  that  under 
those  conditions  the  vessel  is  quite  stable. 

On  arrival  at  the  spot  where  the  rock  has  to  be 
tipped,  the  tug  withdraws  to  a  distance,  taking  with  it 
one  end  of  a  rope,  attached  to  a  valve  on  the  barge. 
When  all  is  ready  this  rope  is  pulled,  and  by  that  means 
a  valve  is  opened,  which  allows  the  compressed  air  to 
force  the  water  in  the  lower  tank  up  into  the  higher 
one,  thereby  upsetting  the  balance  of  things  altogether, 

170 


Curious  Ships 


tipping  the  barge  over,  and  shooting  the  rock  into  the 
water.  A  second  pull  on  the  rope  permits  the  water 
to  run  back  into  the  lower  tank,  when  it  rights  itself. 

This  chapter  can  be  fittingly  concluded  with  a  refer- 
ence to  a  wonderful  little  lightship  recently  constructed 
by  the  "  Corporation  of  Trinity  House/'  that  curious 
survival  from  old  days,  which  is  responsible  for  the 
very  modern  up-to-date  system  of  lighthouses  and 
lightships  around  the  coast  of  England.  It  has  all 
the  attributes  of  an  ordinary  lightship — a  powerful 
occulting  light  placed  at  a  high  elevation — yet  it  can 
be  left  to  itself  without  attention  for  three  months  at 
a  time. 

In  shape  it  is  like  a  lifeboat,  and  in  the  centre  there 
rises  a  four-legged  structure  which  carries  the  light.  This 
is  26  feet  above  the  water,  and  gives  a  flash  of  5100 
candle-power — strong  enough  to  be  seen  10  miles  away. 

In  the  hold  are  four  steel  cylinders  containing  com- 
pressed gas,  enough  to  keep  the  light  burning  day  and 
night  for  100  days.  The  light  itself  is  an  argand  burner, 
but  experiments  are  being  made,  and  probably  an  in- 
candescent burner  and  mantle  will  be  used  eventually. 

A  lightship  of  course,  like  a  lighthouse,  does  not 
show  a  steady  light,  but  a  series  of  tflashes  with  dark 
intervals  between,  and  by  the  frequency  and  duration 
of  these  flashes,  mariners  can  identify  the  different  light- 
ships. One  way  of  producing  these  flashes  is  by  a 
shutter  which  opens  and  closes,  but  that  is  wasteful,  for 
the  light  is  burning  part  of  its  time  in  obscurity.  The 
better  way,  and  the  one  now  generally  adopted,  is  to 
surround  the  light  with  a  lantern  containing  a  series  of 
lenses  and  prisms  which  collect  all  the  light  and  con- 
centrate it  into  beams.  The  lantern  revolves  round  and 
round,  and  of  course  carries  the  beams  of  light  with  it ; 
it  becomes  like  the  hub  of  a  great  wheel,  the  spokes  of 
which  are  made  of  light.  The  distant  observer  can 

171 


Curious  Ships 


only  see  the  light  when  one  of  the  beams  falls  directly 
upon  his  eye,  and  thus  as  the  lantern  turns  round  he 
sees  a  series  of  flashes. 

But  what  turns  the  lantern  round  ?  In  this  case  it 
is  ingeniously  arranged  for  the  gas  to  do  it  itself.  The 
gas,  on  its  way  from  the  cylinder  which  contains  it  to 
the  burner,  passes  through  a  little  motor,  like  a  tiny 
three-cylinder  steam-engine,  and  the  lantern  is  so  deli- 
cately balanced  and  fitted  with  ball-bearings  that  this 
little  engine  can  turn  it  quite  regularly. 

Under  the  lantern  there  hangs  a  large  bell,  which  is 
struck  by  a  hammer  every  time  the  boat  moves  with  the 
force  of  the  waves,  and  so  a  signal  is  made  which  can 
be  heard  in  foggy  weather. 


172 


CHAPTER  XIII 

HOW  BIG  GUNS  ARE  MADE 

IT  is  sad  to  think  that  so  much  refined  skill  and  valuable 
labour  is  expended  upon  devising  machines  whose  ulti- 
mate object  is  killing  people.  Yet  such  is  the  romance 
attaching  to  warfare  that  even  the  most  peaceful  man 
finds  a  great  fascination  in  hearing  about  them. 

It  is  a  remarkable  fact  that  in  the  Crimean  War,  so 
recent  as  to  be  well  remembered  by  many  people  still 
living,  the  guns  used  by  the  British,  at  that  time  un- 
doubtedly the  leading  engineering  nation,  were  only  made 
of  cast  iron,  and  were  of  very  primitive  construction. 
Since  then,  however,  the  chemist  has  succeeded  in 
making  explosives  of  much  greater  power  than  were 
known  in  Crimean  days,  and  the  engineer  and  metal- 
lurgist have  responded  by  producing  guns  of  the  most 
perfect  structure  conceivable  (with  our  present  know- 
ledge) in  which  to  utilise  the  new  explosives. 

The  large  guns  at  present  used  in  the  great  navies  of 
the  world  are  known  as  1 2 -inch  ;  that  being  the 
diameter  of  the  bore.  Guns  of  I3|-inch  bore  are 
under  discussion,  but  many  authorities  consider  that 
seeing  the  1 2-inch  are  able  to  reach  as  great  a  range  as 
is  of  any  practical  use,  the  greater  quickness  with  which 
they  can  be  handled  and  fired,  as  compared  with  the 
I3j-inch,  more  than  compensates  for  the  heavier  pro- 
jectile thrown  by  the  latter.  We  shall  probably  find, 
however,  that  13^-inch  guns  will  be  in  use  before 
long. 

173 


How  Big  Guns  are  Made 

Just  a  word  of  explanation  is  necessary,  at  this  point, 
in  regard  to  explosives.  In  an  earlier  chapter  we  con- 
sidered the  way  in  which  gas  explodes  through  sudden 
expansion  caused  by  heat.  The  explosion  of  a  solid 
or  liquid  is  not  quite  the  same. 

We  know  that  there  are  solids  and  liquids  formed  of 
a  combination  of  elements  which,  if  separated,  at  once 
assume  a  gaseous  and  therefore  more  bulky  form. 
Water,  for  example,  if  split  up  into  its  constituents, 
becomes  oxygen  and  hydrogen,  both  gases  ;  and  while 
there  is  still  exactly  the  same  amount  of  matter  in  both, 
the  gases  occupy  much  more  space  than  the  liquid  did. 
If,  then,  by  some  means,  we  could  separate  water  into 
its  constituent  gases  suddenly,  we  should  cause  an 
explosion. 

In  the  case  of  water  there  is  no  known  means  of 
doing  this,  for  oxygen  and  hydrogen  readily  combine, 
and  are  then  very  loath  to  part,  but  there  are  gases 
which  enter,  very  reluctantly,  into  combinations  of  solid 
or  liquid  form,  and  separate  again  on  the  slightest  provo- 
cation, so  that  a  very  little  thing,  such  as  slight  heat 
or  a  sharp  blow,  will  cause  these  liquids  or  solids  to 
turn  into  gas  with  inconceivable  suddenness  and  with 
almost  irresistible  force.  That,  briefly,  is  the  explana- 
tion of  the  explosion  which  takes  place  in  a  gun. 

The  gun  itself  is  simply  an  enormous  tube,  in  its 
modern  forms  invariably  open  at  both  ends.  One  end, 
however,  called  the  "  breech,"  can  be  securely  closed 
by  a  door  or  stopper  called  the  "  breech-block."  To 
fire  it,  the  "  breech "  is  opened,  the  shell  put  in,  and 
then  the  cartridge  containing  the  explosive.  The 
breech-block  is  then  replaced  and  securely  fastened  ; 
an  electric  spark  or  a  blow  from  a  hammer  fixed  to 
the  breech-block  explodes  the  charge,  and  its  sudden 
expansion  into  gas  drives  the  shell  along  the  tube  and 
out  at  the  muzzle  end  with  great  force. 

*74 


How  Big  Guns  are  Made 

Modern  guns  are  of  great  length.  The  1 2-inch  gun 
of  1864  was  only  about  15  feet  long;  the  1 2-inch 
gun  of  the  present  day  is  over  50  feet  long  ;  it  would 
overtop  the  roof  of  a  three-storey  house,  if  reared  up 
against  it.  This  is  because  the  explosive  pushes  the 
shell  so  long  as  it  is  in  the  gun,  but  ceases  to  do  so  the 
moment  it  has  left  the  muzzle,  so  that  the  advantage  of 
a  long  gun  over  a  short  one  is  exactly  the  same  as  that 
which  a  long-armed  man  has  over  a  man  with  short 
arms  when  throwing  a  cricket-ball.  The  gun  is  made 
sufficiently  long  to  give  the  explosive  time  to  impart 
the  utmost  possible  velocity  to  the  projectile. 

But  the  modern  gun  is  not  a  simple  tube.  The 
British  practice  is  to  make  it  of  three  layers  of  solid 
steel  and  a  layer  of  wire.  First  a  steel  tube  is  made, 
the  full  length  of  the  gun,  and  with  a  bore  of  1 2-inch 
diameter.  It  is  of  a  special  quality  of  steel,  produced 
by  the  addition  of  nickel  and  chromium,  and  hence 
called  "  nickel-chrome  gun-steel."  It  is  formed,  more- 
over, in  a  special  way. 

When  an  ingot  of  steel  is  cast,  as  described  in  an 
earlier  chapter,  certain  impurities  have  a  tendency  to 
collect  together  into  one  place,  and  by  so  doing  they 
form  a  weak  spot  in  the  ingot.  Fortunately,  however, 
they  always  gather  in  that  part  which  sets  last,  which, 
in  the  case  of  a  solid  ingot,  must  be  the  centre.  This 
fact  is  ascertained  in  a  very  interesting  way.  If  an 
experimental  ingot  be  made  and  then  cut  in  two,  and 
its  cut  surfaces  polished,  the  steel  will  look  just  the 
same  all  through  ;  but  if  a  piece  of  ordinary  photo- 
graphic bromide  paper,  moistened  in  sulphuric  acid,  be 
laid  upon  the  polished  surface,  the  chemical  nature  of 
the  impurities  enables  them  to  imprint  themselves  upon 
it,  so  that  a  picture  is  produced  from  which  the  exact 
position  of  the  weak  place  can  be  seen. 

A  solid  octagonal  ingot  is  therefore  cast,  to  start 

175 


How   Big   Guns  are  Made 

with,  and  its  centre  is  then  cut  right  out  ;  in  that  way 
removing  what  is  known  to  be  always  the  weak  place  in 
the  ingot.  Then  this  hollow  ingot  is  forged  under  a 
powerful  hydraulic  press  until  it  is  approximately  the 
right  length  and  diameter,  after  which  it  is  placed 
in  a  lathe,  turned  on  the  outside,  and  bored  on  the 
inside. 

Over  the  first  tube  another  is  made  to  fit  tightly, 
and  then  over  that  the  wire  is  wound.  This  is  more 
correctly  steel  tape,  about  J-  inch  wide  and  -fa  inch 
thick,  and  it  is  of  enormous  strength.  We  can  realise 
this  from  the  fact  that  three  heavy  cart-horses  could  be 
lifted  by  a  single  strand  of  it,  small  though  it  is.  It  is 
wound  on  just  like  cotton  on  a  reel,  except  that  there 
are  only  twelve  layers  at  the  muzzle  end,  increasing  to 
eighty  layers  at  the  breech  end.  Altogether  about 
130  miles  of  wire  are  wound  on  a  1 2-inch  gun. 

Finally,  another  tube  or  jacket  of  steel  forms  the 
outermost  layer  of  all. 

The  breech-block  is  a  most  marvellous  piece  of 
mechanism.  There  are  different  varieties  of  it  made 
by  different  makers,  but  they  are  mostly  like  a  huge 
screw  stopper,  fitting  into  and  entirely  closing  the  end 
of  the  gun.  The  screw  thread  is  not  continuous,  how- 
ever, for  if  it  were,  it  would  take  too  long  to  screw  in, 
but  there  are  rows  of  projections  like  short  threads  on 
the  block  and  corresponding  rows  on  the  inside  of  the 
gun,  so  that  the  block  can  be  pushed  in,  and  then  a 
partial  turn  causes  the  two  sets  of  threads  to  engage 
with  one  another  and  the  block  is  made  quite  fast. 
For  it  is  easy  to  see  that  it  has  to  withstand  the  full 
force  of  the  explosion,  and  so  must  be  very  firmly  fixed. 

If  the  charge  should  be  fired  by  accident  before 
the  breech  was  closed,  the  consequences  would  be  too 
awful  to  contemplate,  but  such  an  occurrence  is  pre- 


How  Big  Guns  are  Made 

vented  by  the  firing  mechanism  being  so  arranged 
that  it  cannot  possibly  be  operated  except  when  the 
breech-block  is  securely  fixed  in  its  place. 

For  convenience  in  opening  and  closing,  the  block 
works  on  hinges  like  a  door,  and  there  is  an  automatic 
arrangement  whereby  the  empty  cartridge-case  is  with- 
drawn and  the  gun  cleaned  by  an  air  blast,  whenever 
the  breech  is  opened. 

When  operated  by  hydraulic  power,  the  breech  of 
a  12-inch  gun  can  be  opened  in  a  little  under  4 
seconds  and  closed  and  properly  secured  in  a  little  over 
4  seconds.  By  hand  it  takes  half  as  long  again. 

The  12-inch  projectile  weighs  850  Ibs.,  and  is  driven 
by  a  charge  of  350  Ibs.  of  cordite ;  it  leaves  the 
muzzle  at  the  rate  of  3000  feet  per  second,  and  at  a 
range  of  about  14  miles  will  pierce  through  wrought 
iron  17  \  inches  thick. 

The  gun  itself  weighs  about  70  tons. 

Large  guns  are  usually  mounted  upon  the  ship  in 
"  barbettes."  Barbette  is  a  very  old  fortification  term, 
and  means  the  platform  on  which  the  men  and  guns 
stood,  behind  the  ramparts  of  a  fort,  so  that  the  guns 
could  be  fired  over  the  ramparts.  On  a  ship  it  means 
the  space  inside  the  protection  of  a  rampart  of  armour 
plate,  in  which  guns  can  be  mounted.  Inside  this 
space  there  stands  a  turret,  a  circular  rotating  fort, 
with  sides  and  roof  of  armour  plate,  in  which  the  guns 
are  actually  placed,  so  that  they  are  entirely  enclosed 
except  for  the  gaps  out  of  which  the  muzzles  project. 
Its  upper  part  is  above  the  edge  of  the  barbette  armour, 
so  that  the  guns  fire  over  it. 

The  turret  is  a  two-storey  arrangement,  on  the  upper 
floor  of  which  are  the  guns,  usually  a  pair,  although 
the  question  of  placing  three  guns  in  one  turret  is  now 
being  considered.  Each  gun  rests  upon  a  cradle,  which 
is  free  to  move  upon  a  strong  steel  slide.  When  it  is 

I77  M 


How  Big  Guns  are  Made 

fired,  and  the  recoil  causes  it  to  slide  backwards,  its 
motion  is  checked  by  a  hydraulic  ram,  or  a  spring 
which  not  only  acts  as  a  buffer,  but,  as  soon  as  the 
recoil  has  spent  its  force,  returns  the  gun  automatically 
to  the  position  for  firing.  The  slide  is  fixed  upon 
pivots  so  that  it  is  capable  of  a  see-saw  movement,  and 
it  can  be  raised  or  lowered  so  as  to  elevate  or  depress 
the  gun  according  to  the  distance  of  the  object  aimed  at. 

The  laying  of  the  gun — that  is,  its  movement  in  a 
horizontal  plane — is  done  by  turning  the  whole  turret. 

From  the  centre  of  the  lower  storey  of  the  turret, 
called  the  working  chamber,  there  is  a  steel  shaft, 
which  reaches  right  down  to  the  magazine  in  the  lower 
part  of  the  ship,  and  in  it  there  are  hoists,  up  which 
the  ammunition  is  sent  to  the  working  chamber.  It  is 
received  by  the  men  there,  and  sent  by  them  up  other 
hoists  to  the  guns,  as  required.  The  working  chamber 
is  entirely  shielded  by  the  thick  armour  of  the  barbette, 
so  that  the  ammunition  is  comparatively  safe  there, 
and  it  only  goes  up  to  the  guns  as  required,  and  is 
loaded  into  the  gun  instantly. 

These  hoists  are  so  arranged  that,  whatever  position 
the  gun  may  be  in,  a  shell  coming  up  will  stop,  auto- 
matically, exactly  opposite  the  breech,  and  a  mechanical 
rammer  can  then  push  it  straight  into  the  gun.  Thus 
the  gun  can  be  loaded  while  it  is  actually  being  moved 
to  alter  the  elevation.  It  is  these  devices  which  explain 
the  otherwise  incredible  fact  that  these  huge  guns  with 
their  85o-lb.  projectiles  can  be  loaded  and  fired  at  the 
rate  of  four  rounds  a  minute. 

With  a  range  of  something  like  fourteen  miles  it  is 
necessary  that  the  "  sights  "  should  be  telescopes.  Open 
sights  on  the  principle  of  those  on  a  rifle  would  be 
quite  useless  for  such  a  distance. 

All  the  movements  of  the  guns  and  turret,  the  hoists 
and  the  rammer,  are  made  by  power,  generally  hydraulic, 


How  Big  Guns  are  Made 

but  sometimes  electric,  or  a  combination  of  both.  They 
can  be  controlled  by  the  simplest  possible  movements 
of  a  handle. 

The  elevation  of  the  gun  depends,  of  course,  upon 
the  distance  of  the  object  aimed  at.  The  farther  away 
it  is,  the  greater  the  elevation.  This  distance  or  range 
is  found  by  instruments  in  the  "range-finding"  station, 
and  from  there  it  is  communicated  to  the  men  in  the 
turrets  by  simple  indicators.  Knowing  the  range,  the 
gunner  sets  his  telescopic  sight  accordingly,  and  then 
sights  his  telescope  exactly  upon  the  object. 

We  can  now  pass  on  to  an  example  of  the  floating 
platforms,  called  battleships,  on  which  such  guns  as 
these  are  placed. 


179 


CHAPTER   XIV 

WAR  VESSELS 
THE    DEADLY    BATTLESHIP 

PAGE  182  shows  us  a  very  remarkable  ship,  one  of  the 
most  powerful  battleships  on  the  waters,  the  Minas 
Geraes,  belonging  to  the  Republic  of  Brazil. 

It  is  of  the  Dreadnought  type,  and  has  been  designed 
and  built  by  the  well-known  firm  of  Sir  W.  G.  Armstrong, 
Whitworth  &  Co.,  Ltd.,  of  Newcastle-on-Tyne. 

I  will  attempt  to  draw  a  pen-picture  of  this  great 
vessel. 

Imagine  a  great  flat  deck,  in  round  figures  500  feet 
long  and  80  feet  wide.  None  of  those  raised  structures 
with  which  we  are  so  familiar  upon  the  deck  of  a 
merchant  ship  are  to  be  seen,  except  in  the  centre, 
where  there  is  a  comparatively  small  "deck-house," 
surrounding  the  two  huge  funnels  and  the  single  tripod 
mast.  Fore  and  aft  the  deck  is  quite  clear,  except  for 
small  things  such  as  bollards,  in  order  that  there  may 
be  nothing  to  interfere  with  the  fire  of  the  guns. 

In  front  of  the  "  deck-house  "  there  are  two  turrets, 
each  containing  two  12 -inch  guns  ;  behind  it  are  two 
more,  while  one  stands  on  either  side  of  it. 

On  its  roof,  forward,  there  is  a  "  conning  "  tower,  a 
small  building  of  armour  plate,  from  the  security  of 
which  the  officers  can  "  con,"  or  watch,  what  is  going 
on  around,  while  just  above  it  is  a  platform  forming 
the  bridge  from  which  the  ship  is  navigated,  and  a 
similar  smaller  tower  stands  upon  the  after  end. 

1 80 


War  Vessels 

Springing  from  near  the  foot  of  the  mast  on  each 
side,  and  supported  from  it,  is  a  light  but  strong  arm, 
from  the  end  of  which  a  boat  is  suspended  so  that  it 
can  be  quickly  dropped  into  the  water,  while  high  up 
on  the  mast  itself  is  a  small  protected  platform,  from 
which  the  firing  can  be  controlled  and  its  effect  more 
easily  seen  than  it  can  be  from  the  deck.  On  the  mast, 
too,  are  yards  for  signalling  and  to  carry  the  wireless 
telegraph  apparatus,  while  dotted  about  and  peeping 
through  holes  in  the  side  of  the  ship  are  many  smaller 
guns. 

In  order  to  appreciate  the  "  points  "  of  a  battleship, 
it  is  necessary  first  of  all  to  understand  the  conditions 
which  control  the  design  of  such  a  vessel. 

Primarily,  she  is  a  floating  fortress,  a  platform  upon 
which  powerful  guns  can  be  mounted.  In  ships  of  the 
Dreadnought  type  there  are^  either  ten  or  twelve  1 2-inch 
guns  ;  in  this  particular  one  there  are  twelve,  and  it  is 
clear  that,  other  things  being  equal,  the  more  there  are 
the  better.  But  every  pair,  with  the  turret  in  which  they 
are  mounted  and  the  necessary  machinery  for  working 
them,  weighs  500  tons,  and  the  "barbette  armour" 
with  which  they  are  protected  weighs  another  100  tons, 
making  600  tons  in  all.  Thus  twelve  guns  will 
represent  a  load  of  3600  tons  for  the  ship  to  carry. 

Then  it  must  be  capable  of  developing  a  high  speed, 
for  it  is  quite  evident  that  the  ship  or  squadron  which 
can  move  the  fastest  will  be  able  to  choose  the 
conditions  under  which  to  fight,  and  fight  only  in 
circumstances  favourable  to  itself.  This  necessitates 
engines  and  boilers  of  ample  power,  and  consequently 
of  great  weight.  Sufficient  coal  must  be  carried,  too, 
to  enable  the  ship  to  travel  a  distance  from  its  base 
without  the  risk  of  being  "  becalmed "  through  lack  of 
fuel. 

Finally  the  ship  must  be  protected  with  armour  to 

181 


War  Vessels 

resist  the  enemy's  guns,  and  when  we  remember  that 
that  is  sometimes  12  inches  thick  it  is  easy  to  see 
that  it,  too,  represents  an  enormous  load  upon  the  ship. 

It  is  clear,  then,  that  a  vessel  of  this  type  must  be 
a  series  of  compromises.  She  must  have  as  many  guns 
as  possible,  and  must  be  as  thickly  armoured  as 
can  be,  but  neither  of  these  must  be  so  heavy  as  to 
impair  the  speed.  In  the  same  way,  the  weight  allowed 
for  offensive  purposes  (in  the  guns)  must  not  be 
unduly  increased  at  the  expense  of  the  weight  of 
defensive  armour  or  vice  versa.  All  these  and  various 
other  considerations  have  to  be  taken  into  account  and 
balanced  one  against  another,  and  it  is  apparent  what 
endless  scope  they  afford  for  differences  of  opinion  and 
for  keen  discussion. 

There  are  also  certain  considerations  peculiar  to 
different  nations.  For  instance,  the  patriotic  Briton 
may  be  grieved  to  hear  that  whereas  the  Minas  Geraes 
carries  twelve  heavy  guns,  Great  Britain  does  not 
possess  a  ship  with  more  than  ten  1 2-inch  guns. 
One  does  not,  of  course,  know  exactly  what  was  in  the 
minds  of  the  respective  designers,  but  the  difference 
may  be  due  to  the  fact  that  Britain,  being  the  premier 
naval  power,  would,  in  the  event  of  being  involved  in 
a  naval  war,  almost  certainly  be  the  attacking  party. 
The  scene  of  operations  would  probably  be  somewhere 
near  the  enemy's  coast-line,  and  so  British  ships  need 
to  be  designed  to  have  a  greater  range  of  action  than 
those  of  other  nations.  Moreover,  as  will  be  seen 
presently,  the  Minas  Gemes,  while  she  has  the 
maximum  number  of  guns,  has  to  pay  for  the  fact  by 
having  comparatively  thin  armour,  an  arrangement 
which  may  perhaps  be  justified  by  the  probable  con- 
ditions of  a  naval  war  in  South  America. 

The  modern  battleship  has  a  "primary  armament,"  as 
it  is  termed,  of  heavy  guns,  all  the  same  size,  for  use 

182 


Jly  permission  of  the  Brazilian  Naval  Commissi 


THE  "  MINAS  GERAES  " 

A  battleship  of  the  "  Dreadnought"  type,  built  at  Newcastle  for  the  Brazilian  Government. 
It  is  the  first  ship  that  ever  fired  ten  of  the  largest  guns  simultaneously. 


*:."*:•.•  'Hod  A  -c 


War  Vessels 

against  ships  of  its  own  class,  and  a  "  secondary 
armament "  of  lighter  weapons,  for  repelling  an  attack 
by  torpedo  craft. 

The  arrangement  of  the  heavy  guns  is  a  very 
important  matter,  for  they  must  be  so  placed  that  as 
many  as  possible  can  be  fired  simultaneously  in  the 
same  direction.  The  diagram  (Fig.  37)  shows  how  they 
are  arranged  on  the  Minas  Geraes,  each  of  the  circles 
representing  a  barbette  in  which  a  turret  revolves. 
Four  of  these  are,  it  will  be  seen,  upon  the  centre  line 
of  the  ship,  two  forward  and  two  aft.  Of  the  two  in 
front,  the  hindmost  is  on  a  higher  level,  so  that  its 
guns  can  fire  over  the  top  of  the  other  ;  they  can  also 
be  rotated  so  that  the  guns  can  be  fired  to  either  side. 
The  two  turrets  at  the  rear  of  the  ship  are  arranged  in 
a  precisely  similar  way. 

Then  there  is  the  turret  on  either  side,  whose  normal 
position  is  with  the  guns  pointing  out  over  the  side  of 
the  ship,  but  which  can  be  rotated  so  that  they  can 
be  fired  fore  and  aft.  Thus  we  see  that  eight  guns 
can  be  fired  simultaneously  forward,  and  eight  guns 
aft,  but  ten  can  be  fired  to  either  side.  This  ship 
was  the  first  to  fire  ten  1 2-inch  guns  on  the  broad- 
side. 

It  will  be  noticed  that  two  guns  (those  in  one  of  the 
side  turrets)  will  always  be  out  of  action,  unless  the  ship 
be  attacked  on  both  sides  at  once,  a  state  of  affairs 
which  good  seamanship  would  avoid,  so  that  the  effective 
armament  may  be  said  to  be  only  ten  guns.  The  ideal 
arrangement  would  be  to  keep  the  deck  of  the  ship 
quite  clear,  so  that  the  side  turrets  could  be  turned 
right  round  and  all  guns  fired  to  either  side.  This  is 
rendered  difficult  because  of  the  presence  of  the 
funnels,  mast,  and  other  necessary  structures  on  the 
deck,  but  it  has  been  managed  on  some  of  the  British 
ships  now  under  construction  and  also  on  some  of  the 

183 


War  Vessels 


12  Guns.— 
8  can  fire  forward. 
8    ,        ,   aft. 


10 


on  either  broadside. 


10  Guns. — 
8  can  fire  forward. 
6    „     „    aft. 
8    ,,     ,,    on  either  broadside. 


10  Guns. — 

4  can  fire  forward. 

4    „     „   aft. 
10    ,,     „  on  either  broadside. 

FIG.  37.— Various  arrangements  of  the  heavy  guns  on  a  Dreadnought  battle- 
ship. 

Each  circle  represents  a  turret,  with  two  guns. 

Those  marked  H  are  on  a  higher  level  than  the  others. 

In  some  of  the  latest  ships  the  structures  on  the  deck  are  so  arranged,  that 
the  midship  guns  can  be  fired  to  either  side. 

184 


War  Vessels 

United  States  battleships,  which  will  be  able  to  fire  all 
their  ten  guns  on  either  broadside. 

This  result  is  achieved  by  lengthening  the  ship  some- 
what, and  placing  all  five  turrets  on  the  centre  line, 
the  second  and  fourth  being  higher  than  the  others,  as 
shown  in  the  diagram  (Fig.  37).  Under  this  arrange- 
ment four  guns  can  be  fired  fore  or  aft,  but  the  whole 
ten  on  either  broadside. 

The  guns  on  the  Minos  Geraes  are  operated  by 
hydraulic  power  in  all  their  movements  except  the 
turning  of  the  turrets,  which  is  done  by  electricity, 
and  in  every  case  emergency  gear,  either  hydraulic 
or  hand  power,  is  provided  so  that  should  one  set  of 
apparatus  be  thrown  out  of  order,  another  can  be  used. 

The  magazines  are  kept  cool  by  a  draught  of  cold  air 
produced  by  a  refrigerating  machine  capable  of  cooling 
300,000  cubic  feet  of  air  per  hour. 

The  secondary  armament  consists  of  twenty-two 
4»7  inch  guns  and  six  3-pounders,  that  is,  guns  which 
fire  a  projectile  weighing  3  Ibs.  Fourteen  of  the 
former  are  placed  in  casemates — that  is  to  say,  they  fire 
through  holes  in  the  armoured  sides  of  the  ship — while 
the  other  eight  are  located  in  suitable  positions  on  the 
deck-house,  each  behind  its  own  armour  shield. 

The  3-pounders  are  placed,  some  on  the  deck-house 
and  some  on  the  roofs  of  the  turrets  which  contain 
the  1 2 -inch  guns. 

The  sides  of  the  ship,  from  the  top  to  5  feet  below 
the  water  line,  are  covered  with  armour  plate.  In 
the  centre,  where  the  engines  and  magazines  are,  this 
is  9  inches  thick,  but  over  the  less  vulnerable  parts  it 
is  only  6  inches  and  in  some  places  4  inches. 

There  are  two  triple-expansion  engines,  which 
develop  about  25,000  horse-power,  and  are  capable  of 
driving  the  ship  at  a  speed  of  2 1  knots.  The  huge 
size  of  each  of  these  will  be  realised  from  the  dimensions 

185 


War  Vessels 

of  the  cylinders.  The  high-pressure  is  39  inches 
diameter  ;  from  that  the  steam  passes  to  the  inter- 
mediate-pressure cylinder,  63  inches  diameter,  and  from 
that  it  divides  and  goes  to  two  low-pressure  cylinders, 
each  73  inches  in  diameter.  The  stroke  of  the  piston 
is  in  each  case  3  feet  6  inches.  The  steam  is  generated 
in  eighteen  water-tube  boilers. 

Although  this  recently-built  ship  is  fitted  with  reci- 
procating engines,  it  is  quite  exceptional  now  for  large 
warships  not  to  have  turbines,  either  of  the  Parsons 
or  Curtis  type. 

CRUISERS 

The  battleships  of  a  fleet  may  be  likened  to  the 
infantry  in  an  army.  They  bear  the  heaviest  part 
of  the  fighting ;  comparatively  slow  in  movement, 
they  are  capable  of  dealing  and  receiving  the  hardest 
blows. 

The  cruisers  are  more  like  the  mounted  infantry, 
for  they  are  faster  but  less  heavily  armed,  and  not 
so  securely  protected.  The  largest  type  of  cruisers 
afloat  are  almost  as  great  a  tonnage  as  the  largest 
battleships,  but  they  have  only  eight  1 2-inch  guns 
against  the  battleship's  ten  or  twelve,  and  their  thickest 
armour  is  only  8  inches  thick  as  compared  with  10, 
n,  or  12  inches.  On  the  other  hand,  they  could  beat 
a  first-class  battleship  in  a  race  by  at  least  4  knots 
an  hour. 

Indeed,  there  are  building  for  the  British  Navy  two 
large  cruisers  which  will  be  larger  than  any  battleship 
yet  proposed,  for  their  tonnage  will  be  about  26,000, 
with  turbines  of  over  70,000  horse-power,  and  a  speed 
of  28  knots ;  whereas  the  largest  battleship  building 
is  only  22,500  tons,  with  a  speed  of  21  knots. 

But  cruisers  are  not  all  of  this  large  type.  There 
are,  indeed,  a  great  variety  of  them,  down  to  quite  small 

186 


War  Vessels 

vessels,  each  particular  type  having  its  special  purpose 
in  warfare.  Of  course,  as  the  size  of  the  ship  diminishes, 
the  size  of  the  guns  is  reduced  too. 

THE  FASTEST  SHIPS  AFLOAT 

Another  very  interesting  class  of  naval  vessel  is  the 
"destroyer."  Its  name  arose  in  this  way.  The 
invention  of  the  torpedo  was  followed  by  the  construc- 
tion of  torpedo-boats,  small  vessels  armed  with  tubes 
for  launching  torpedoes,  whose  method  of  warfare  is 
to  creep  up  to  a  larger  vessel  under  cover  of  night  or 
by  some  subterfuge  and  endeavour  to  cripple  it  with 
one  well-directed  torpedo. 

Now  a  new  weapon  or  mode  of  attack  always  calls 
forth  an  answer,  and  the  answer  in  this  case  was  the 
torpedo-boat  destroyer,  a  vessel  a  little  larger  than 
the  torpedo-boat,  with  a  few  light  guns  powerful 
enough  to  sink  the  smaller  craft,  and  of  enormous 
speed.  Its  primary  duty  is,  therefore,  to  chase  the 
torpedo-boats  and  drive  them  off  the  sea,  but  its 
great  speed  makes  it  a  very  useful  vessel  for  scouting 
and  similar  purposes  as  well.  It  is  also  provided  with 
tubes,  so  that  it  can  launch  torpedoes  itself  on  occasion. 

A  destroyer  usually  has  two  or  four  huge  funnels  and  a 
single  mast,  and  is  generally  one  of  the  ugliest  of  vessels. 
It  has  nothing  in  the  nature  of  armour,  but,  on  the 
contrary,  is  built  of  the  thinnest  plates  possible.  At 
first  the  designers  appear  to  have  gone  a  little  too  far 
in  this  direction,  for  one  of  the  early  British  destroyers 
was  completely  lost  in  the  North  Sea,  and  there  seems 
to  be  little  doubt  that  she  simply  broke  in  two  owing  to 
the  extreme  lightness  of  her  structure,  and  went  to  the 
bottom  like  a  lump  of  iron. 

This  extreme  lightness  is  in  order  that  the  maxi- 
mum of  engine-power  can  be  got  on  board.  The 


War  Vessels 

latest  type  of  destroyer  is  of  1000  tons  only,  yet 
her  engines,  which  are  Parsons  turbines,  can  develop 
15,500  horse-power,  that  is,  15 J  horse-power  to 
the  ton,  whereas  in  the  largest  cruisers  the  engine- 
power  is  less  than  3  horse-power  to  the  ton.  Prac- 
tically every  other  consideration  is  sacrificed  for 
speed,  with  the  result  that  a  rate  of  over  40  miles 
an  hour  is  attained  by  some  of  these  vessels  (see 
opposite).1 

SUBMARINE  BOATS 

But  perhaps  the  most  fascinating  of  all  boats  to 
the  general  reader  is  the  submarine.  There  is  a 
romance  and  mystery  about  it  which  makes  it  very 
attractive. 

The  purpose  of  a  submarine  boat  is  to  attack  a 
larger  vessel  by  means  of  torpedoes,  without  the 
latter  being  aware  of  its  presence.  For  example, 
two  hostile  ships  approach  each  other.  Concealed 
behind  one  of  them  is  a  submarine,  and  as  soon  as 
it  gets  within  a  suitable  distance  it  dives  below  the 
surface,  proceeds  to  the  other  vessel,  and  quite  un- 
suspected, probably,  launches  its  deadly  torpedo. 
Though  itself  invisible,  its  officers  can  see  what  is 
going  on  around  by  means  of  a  small  tube  which 
projects  above  the  surface,  and  by  a  series  of  re- 
flectors and  lenses  shows  them  a  picture  of  the 
surrounding  objects,  and  so  enables  them  to  stalk 
their  prey.  This  tube  is  called  the  "  periscope." 

Needless  to  say,  a  submarine  has  no  deck  in  the 
ordinary  sense  of  the  term ;  in  fact,  her  form  is 

1  In  this  connection  it  may  be  interesting  to  state  that  a  knot,  or  nautical 
mile,  in  which  the  speed  of  ships  is  usually  given,  is  one  minute  of 
longitude  measured  along  the  equator ;  in  other  words,  ^rhnrth  °f  the 
earth's  circumference.  Ten  knots  are  equal  to  about  ii£  statute  miles,  so 
that  15  per  cent,  added  to  the  number  of  knots  gives  approximately  the 
equivalent  in  ordinary  miles. 

188 


n      «». 


War  Vessels 

approximately  that  of  a  fish,  but  there  is  a  nearly 
flat  part  with  a  light  handrail  where  the  crew  can 
get  a  little,  very  little,  exercise  when  the  boat  is  on 
the  surface.  At  one  point  on  the  submarine's  "  back  " 
there  is  a  small  "conning"  tower,  and  it  is  through 
it  that  the  crew  pass  in  and  out.  When  it  is  necessary 
to  descend  below  the  surface  the  "  hatch  "  at  the  top  of 
the  tower  is  of  course  closed.  There  is  also  another 
"  hatch  "  on  the  back  of  the  boat,  through  which  the 
torpedoes  are  taken  on  board. 

The  engines  are  of  the  "  internal-combustion  "  kind, 
and  are  generally  driven  by  paraffin  or  some  other 
similar  oil,  and  there  are  usually  two  propellers.  The 
engines  can,  however,  only  be  used  when  the  ship  is  on 
the  surface,  for  they  would  use  up  the  air  and  soon 
suffocate  the  crew  if  worked  under  water.  Electric 
motors  are  therefore  provided  to  turn  the  screws,  and 
the  engines,  when  the  ship  is  on  the  surface,  can  be 
made  to  charge  electric  accumulators,  which  supply  the 
current  to  drive  the  motors  when  she  is  submerged. 

The  boat  is  caused  to  sink  in  the  water  by  very 
simple  means.  There  are  tanks  on  board  which  are 
normally  filled  with  air.  When  it  is  desired  to  sink, 
water  from  the  sea  is  pumped  into  these,  the  air  be- 
coming compressed  into  a  much  smaller  space,  and 
the  weight  of  this  water  causes  the  boat  to  descend. 
To  rise,  all  that  is  necessary  is  to  open  a  valve  and 
allow  the  compressed  air  to  force  the  water  out  again. 
The  air  then  fills  the  tanks  as  before,  and  the  boat 
ascends  to  the  surface. 

To  keep  the  boat  level  when  under  water,  there  are 
horizontal  rudders  and  fins  on  the  sides,  and  in  some 
cases  tanks  containing  water  ballast  at  both  ends,  and  a 
pipe  connecting  the  two.  If  one  end  of  the  boat  floats 
a  little  higher  than  the  other,  a  pump  transfers  a  little 
water  to  the  higher  end  from  the  lower,  and  so  the 

189 


War  Vessels 

vessel  can  be  perfectly  balanced,  and  kept  on  an  even 
keel.  The  action  of  the  pump  can  be  controlled  by  a 
pendulum,  and  so  the  balancing  be  made  quite  auto- 
matic. To  prevent  the  men  being  suffocated  during  a 
long  submersion,  a  supply  of  compressed  air  or  oxygen 
is  carried,  and  also  chemicals  to  remove  the  carbonic 
acid  gas  produced  by  breathing. 

The  working  of  a  submarine  is  a  very  risky  business, 
and  there  have  been  many  catastrophes  connected  with 
them.  It  is  easy  to  see  that  some  accident,  such  as  a 
collision,  may  happen  which  will  let  water  into  the  boat, 
and  so  prevent  it  from  rising  to  the  surface,  and  one 
does  not  need  great  imaginative  powers  to  be  able  to 
picture  the  terrible  plight  of  the  crew,  practically  buried 
alive — quite  safe,  perhaps,  for  the  moment,  but  knowing 
that  in  a  short  time  they  must  all  be  suffocated.  It 
will  be  interesting,  then,  to  see  the  provisions  made  for 
the  men's  escape  in  such  a  case.  Many  devices  have 
been  invented  and  tried,  but  we  shall  only  have  space 
for  one,  which  has  been  adopted  in  the  British  Navy. 

If  the  hole  in  the  submarine  caused  by  the  collision 
is  anywhere  except  in  the  top,  the  water  cannot  entirely 
fill  it,  for  a  certain  amount  of  air  will  be  entrapped  in 
the  upper  part  of  the  vessel,  and  in  that  air-filled  space 
the  men  can  live.  To  provide  against  the  case  of  a 
hole  right  in  the  top,  where,  owing  to  its  very  nature,  it 
is  extremely  likely  to  be  hit,  two  vertical  partitions  are 
fixed  to  the  roof  and  extend  some  little  way  downwards, 
as  shown  in  the  diagram  (Fig.  3  8),  and  these  form  pockets 
in  which  air  will  be  entrapped  under  almost  any  con- 
ceivable conditions.  This  air-space,  however,  will  not 
save  the  men  ;  it  will  only  provide  them  with  a  place 
of  refuge  in  which  to  make  their  preparations  for  escape. 

In  each  of  the  air-pockets,  special  helmet-jackets  are 
provided — one  for  each  man  (see  page  192).  Each 
consists  of  a  helmet, 'large  enough  to  go  over  a  man's 

190 


War  Vessels 

head,  and  leave  him  room  to  move  it  freely  inside, 
connected  to  a  jacket  of  strong  waterproof  material,  with 
sleeves,  and  a  waist-belt.  In  the  front  of  the  helmet 
is  a  window  out  of  which  the  man  can  see,  and  in  a 
pocket  of  the  jacket  is  a  small  can  containing  certain 
chemicals.  The  dampness  of  the  man's  breath  causes 
one  of  the  chemicals  to  give  off  oxygen,  while  the  other, 
at  the  same  time,  absorbs 
carbonic  acid.  Thus  the 
air  in  the  helmet  is  con- 
tinuously re-oxygenated 
and  purified,  and  so  the 
man  can  go  on  breathing 
it  over  and  over  again. 
The  apparatus,  moreover, 
only  weighs  16  Ibs.,  so 
that  the  air  imprisoned 
in  it  is  enough  to  make 
it  act  as  a  lifebuoy,  and 
enable  the  wearer  to  float 


FIG.  38.— Section  of  a  submarine,  show- 
ing the  air-tight  pockets  for  en- 
trapping the  air  and  giving  the  men 
a  chance  to  escape  if  the  boat  be 
"  holed  "  at  the  top.  Suppose  the 
hole-is  at  A,  the  whole  boat  will 
fill,  except  the  two  compartments 
C  C,  where  the  men  can  find  a 
temporary  refuge  in  which  to  pre- 
pare for  their  escape. 


easily. 

As  soon  as  the  men 
have  their  jackets  on  they 
are  comparatively  safe,for 
they  cannot  be  drowned. 
They  can  then,  without 
haste  or  confusion,  open  the  lid  in  the  top  of  the 
"  conning  tower,"  or  the  "  torpedo  hatch,"  and  climbing 
through  it  one  at  a  time  float  gently  up  to  the  surface. 

But  the  wonders  of  this  ingenious  contrivance  have 
not  yet  been  all  told.  In  one  part  the  jacket  is  double, 
and  forms  a  sort  of  bag,  which  on  arriving  at  the 
surface  the  man  can  inflate  by  blowing  into  it.  Thus 
he  forms  a  lifebelt  around  him,  and  he  can  then  open 
the  window  in  his  helmet  and  breathe  the  fresh  air 
again.  This  is  necessary  unless  he  be  rescued  quickly, 

191 


War  Vessels 

for  the  chemicals  cannot  go  on  purifying  the  atmos- 
phere indefinitely.  The  helmet  will,  however,  keep  a 
man  alive  for  nearly  an  hour. 

One  great  advantage  of  these  helmet-jackets  is  that 
the  men  can  practise  in  them,  and  then,  in  the  event 
of  an  accident,  they  have  only  to  do  something  which 
they  have  often  done  before,  and  are  quite  used  to.  In 
the  Naval  Dockyard  at  Portsmouth  (England)  a  large 
tank  has  been  constructed,  with  a  structure  at  the 
bottom  which  represents  a  sunken  submarine.  Men 
being  trained  for  work  on  these  boats  are  lowered 
down  by  a  sort  of  lift  to  the  bottom.  There  they 
array  themselves  in  the  apparatus,  get  out  of  the  lift 
cage,  enter  the  "  submarine,"  and  find  their  way  to 
the  conning  tower,  up  which  they  climb,  finally  open- 
ing the  hatch  at  the  top  and  floating  up  to  the  sur- 
face. Thus  the  conditions  of  a  submarine  sunk  at  the 
bottom  of  the  sea  are  almost  exactly  reproduced,  and 
the  men  become  quite  familiar  with  what  they  are  to 
do  in  an  emergency. 

In  conclusion  it  may  be  interesting  to  state  that 
what  is  believed  to  be  the  largest  submarine  boat  afloat, 
the  British  "  D  i,"  is  of  800  tons  displacement;  it  can 
travel  16  knots  an  hour  on  the  surface  or  10  knots  an 
hour  submerged. 

In  concluding  this  chapter,  a  few  words  on  tor- 
pedoes may  be  of  interest,  for  it  is  not  only  torpedo- 
boats  which  are  armed  with  them,  since  practically 
all  war-vessels,  including  the  largest,  have  torpedo  tubes. 

A  torpedo  is  really  a  small  automatic  submarine 
boat.  It  is  shaped  something  like  a  cigar,  and  has  a 
small  screw-propeller  driven  by  a  compressed  air 
motor,  the  air  being  stored  in  a  chamber  inside  the 
torpedo  itself,  and  it  has  automatic  rudders,  which 
cause  it  to  maintain  a  predetermined  depth  below  the 

192 


By  permission  of  Messrs.  Siebe,  Gor 

A  LIFE-SAVING  HELMET  AND  JACKET 

This  apparatus  enables  men  to  escape  in  safety  from  a  sunken  submarine.  The  man 
has  risen  to  the  surface,  inflated  his  jacket  so  that  he  cannot  sink,  and  opened  the  window 
of  his  helmet  so  that  he  can  breathe  fresh  air. 


War  Vessels 

surface.  In  the  front  part  is  a  quantity  of  high 
explosive  which  is  fired  by  a  mechanical  device  the 
moment  the  nose  of  the  torpedo  strikes  anything. 

The  accounts  of  the  Russo-Japanese  war  raised 
considerable  doubts  as  to  the  efficiency  of  torpedoes, 
and  several  Governments  have  been  trying  experiments 
for  themselves.  One  of  the  most  important  of  these 
was  carried  out  by  Italy.  An  old,  out-of-date  battle- 
ship was  used,  and  it  is  interesting  to  know  that  she  is 
one  of  those  which  made  some  sensation,  years  ago, 
through  carrying  io5-ton  guns.  A  torpedo  was  fixed 
to  her  side  so  as  to  reproduce  as  nearly  as  possible  the 
conditions  which  would  arise  if  a  ship  were  struck  in 
precisely  the  right  spot,  and  then  it  was  fired  by 
electricity.  Instantly  the  ship  began  to  heel  over,  and 
quickly  sank.  At  the  bottom  she  still  remains,  but 
divers  who  have  been  down  report  that  a  hole  of  fifty 
square  metres  in  area  was  torn  in  her  side  by  the 
explosion,  a  fairly  conclusive  proof  of  the  efficacy  of 
the  torpedo  if  properly  directed. 


193  N 


CHAPTER  XV 

SUBMARINE    DIVING 

IT  is  quite  a  natural  transition  to  pass  from  the 
submarine  boat  to  the  submarine  man. 

The  diver's  work  is  becoming  daily  of  increasing 
importance.  Every  warship,  for  example,  now  carries 
men  trained  as  divers,  who  can  go  down  to  clear  a 
propeller  if  it  should  get  entangled  with  a  rope,  or  to 
scrape  the  ship  if  it  should  have  become  foul  during  a 
long  cruise.  Such  great  undertakings  as  the  large 
Breakwater  at  Dover  Harbour  are  carried  out  largely 
by  divers,  while  without  them  many  a  valuable  wreck 
would  be  entirely  lost  which  with  their  aid  can  be 
recovered. 

The  ordinary  diver's  dress  consists,  first  of  all,  of  a 
strong  metal  helmet.  This  completely  envelops  his 
head,  but  it  has  three  glass  windows  through  which  he 
can  see.  It  is  fixed  to  a  metal  corselet  or  breastplate 
which  covers  his  shoulders  and  breast.  This  in  turn 
is  attached  to  a  water-tight  suit  completely  covering  the 
man's  body  ;  except  his  hands,  which  project  through 
elastic  cuffs  which  make  a  water-tight  joint  round  his 
wrists. 

Air  is  forced  by  a  pump  down  a  flexible  tube,  and 
enters  at  the  back  of  the  helmet,  afterwards  escaping 
through  a  little  valve  so  constructed  that,  while  it  will 
let  air  out,  it  will  not  permit  water  to  get  in.  Thus 
the  man  is  provided  with  a  supply  of  fresh  air ;  more- 
over, the  air  prevents  him  from  being  crushed  by  the 

194 


Submarine  Diving 

pressure  of  the  water.  The  pressure  which  exists 
under  water  is  due  to  the  weight  of  water  lying 
above,  and  consequently  it  increases  as  you  descend. 
Approximately  every  2  feet  in  depth  produces  a 
pressure  of  i  Ib.  per  square  inch,  so  that  at  a 
depth  of  70  feet,  for  example,  the  water  presses 
upon  a  diver  with  a  force  of  about  35  Ibs.  on  every 
square  inch  of  his  body.  This  acting  upon  his  chest 
—for,  of  course,  his  suit  is  quite  flexible  —  would 
prevent  him  from  breathing  ;  it  would  be  equivalent  to 
lying  on  one's  back  with  a  35-lb.  weight  on  every 
square  inch  of  one's  chest. 

The  water,  however,  presses  upon  the  little  valve 
mentioned  just  now,  and  prevents  it  opening  to  let  out 
any  air  until  the  pressure  of  the  air  inside  the  suit  is 
equal  to  the  pressure  outside,  and  therefore  the  air 
keeps  the  dress  distended  and  prevents  the  water 
squeezing  the  man. 

On  the  face  of  it,  it  seems  as  if  this  would  simply  be 
changing  one  evil  for  another,  and  that  the  air  pressure 
would  have  the  same  effect  as  the  water.  It  is  not  so, 
however,  for  whereas  the  water  pressure  is  outside  the 
man's  body  only,  the  air  pressure  is  inside  his  lungs  as 
well.  The  outward  pressure  due  to  the  air  in  his  lungs 
balances  the  inward  pressure  of  the  air  around  him, 
and  so  they  neutralise  each  other  and  he  is  able  to 
breathe  freely. 

The  quantity  of  air  contained  in  his  dress  makes  the 
diver  buoyant,  and  he  needs  to  be  weighted  so  that 
he  can  descend  and  stand  firmly  on  the  bottom.  He 
has  40  Ibs.  of  lead  slung  across  his  chest  and  40  Ibs. 
more  on  his  back,  while  his  boots  have  lead  soles 
weighing  16  Ibs.  each.  Even  then,  however,  if  he  is 
careless,  and  lets  his  dress  become  too  much  inflated 
with  air,  he  soars  up  to  the  surface  like  a  balloon. 

The  diver  is  usually  connected  with  the  surface  by  a 

195 


Submarine  Diving 


rope  called  the  "  life-line  "  as  well  as  by  the  air-pipe, 
and  embedded  in  this  rope  there  are  often  telephone 
wires  connected  to  an  instrument  inside  the  helmet  so 
that  the  diver  can  talk  freely  with  his  mates  above. 

There  is  usually  another  rope,  called  the  "  shot- 
rope/'  which  is  tied  to  a  heavy  weight  sunk  at  the 
bottom,  and  forms  a  kind  of  hand-rail  by  which  he 
lowers  himself  down  and  pulls  himself  up.  Still 
another  line  is  attached  to  the  bottom  end  of  this, 
called  the  "  distance-line/'  the  purpose  of  which  is  to 
prevent  him  losing  his  way  when  moving  about  below. 
He  keeps  the  "  distance-line  "  in  his  hand  wherever  he 
may  go,  and  when  he  wants  to  ascend  he  simply 
follows  the  line,  which,  of  course,  leads  him  back  to 
the  "shot-rope." 

Let  us  now  watch  a  diver  dress  himself  preparatory 
to  going  down.  He  first  of  all  arrays  himself  in  plenty 
of  thick  woollen  garments.  Then,  with  the  assistance 
of  an  attendant,  he  gets  into  the  diving  dress,  pushing 
his  hands  through  the  elastic  cuffs,  which  grip  tightly 
round  his  wrists.  His  boots  are  put  on  for  him,  and 
then  the  corselet  or  breastplate.  This  latter  has  a 
loose  ring  all  round  its  edge,  fixed  on  by  screws.  The 
edge  of  the  dress  is  placed  under  this,  and,  when  the 
screws  have  been  tightened  up,  it  is  firmly  gripped 
and  the  joint  made  quite  water-tight.  Finally  the 
helmet  is  screwed  down  on  to  the  corselet,  and  the 
man  is  ready  to  descend. 

The  greatest  depth  at  which  a  diver  has  actually 
done  work  is  210  feet.  Within  about  this  limit  descent 
is  easy  and  safe,  so  long  as  proper  precautions  are 
taken.  The  greatest  danger  arises  from  a  too-quick 
descent  or  ascent. 

Air,  of  course,  is  very  elastic  and  easily  compressed. 
For  example,  at  a  pressure  of  15  Ibs.  to  the  inch  it 
has  only  half  the  volume  that  it  has  when  it  is  free, 

196 


Submarine  Diving 


so  that  when  a  diver  has  descended  to  30  feet  he 
needs  to  have  twice  the  quantity  of  air  in  his  suit,  to 
keep  it  properly  distended,  than  he  does  when  he  is  at 
the  surface.  It  takes  time,  however,  for  the  air-pump 
to  supply  this  extra  air,  and  so  if  he  descends  too 
quickly  he  will  get  "  nipped "  by  the  pressure  of  the 
water.  If  he  is  climbing  down  and  feels  the  pressure 
increasing,  he  has  only  to  stop  a  little  while  and  wait 
for  more  air  ;  but,  if  he  should  by  any  chance  fall,  he 
will  not  be  able  to  save  himself  from  a  squeeze  which 
may  injure  him  seriously.  Since,  however,  he  can  be 
suspended  in  the  water  by  the  life-line  and  air-pipe,  a 
serious  fall  can  only  occur  if  his  attendants  are  grossly 
careless. 

It  seems  strange  at  first  sight,  but  a  much  greater 
danger  attends  a  rapid  ascent  than  a  rapid  descent. 

The  effervescence  of  soda-water  is  a  phenomenon 
familiar  to  every  one.  It  is  due  to  the  fact  that  liquids 
are  capable  of  dissolving  gases  to  a  certain  extent,  and 
the  greater  the  pressure  the  greater  is  the  quantity  of 
gas  which  they  can  dissolve.  Now  soda-water  is  water 
under  pressure  in  a  bottle,  and  in  it  is  dissolved  a 
quantity  of  carbonic-acid  gas.  As  soon  as  the  cork 
is  taken  out,  the  pressure  falls  and  the  water  is  then 
unable  to  hold  as  much  gas  as  it  did  before,  and  so 
the  gas  comes  bubbling  up  to  the  surface. 

The  human  blood  can  absorb  gases  just  like  any 
other  liquid,  and  when  a  diver  is  at  work  the  extra 
pressure  of  the  air  which  he  breathes  causes  the  blood 
to  dissolve  an  abnormal  quantity  of  air,  which,  if  the 
pressure  be  suddenly  removed,  will  bubble  out  of  it 
much  as  the  gas  does  out  of  soda-water.  This  would 
result  in  air  bubbles  being  formed  in  the  tissues  of  the 
body,  possibly  in  the  heart  itself,  causing  serious  illness 
and  perhaps  death.  A  diver  must,  therefore,  come  up 
slowly,  so  as  to  decompress  himself  gradually,  and 

197 


Submarine  Diving 


allow  the  dissolved  air  to  escape  from  his  blood  by 
degrees.  Strange  though  it  may  seem,  a  man  who 
has  come  up  from  a  great  depth  too  quickly — as,  for 
instance,  if  he  be  "  blown-up  "  through  too  much  air 
getting  into  his  dress — must,  although  perhaps  in- 
sensible, be  sent  down  again  instantly,  and  then  drawn 
up  gradually.  Or  sometimes  a  "  recompression  cham- 
ber" is  kept  in  readiness — a  steel  cylinder  in  which 
the  man  can  be  placed,  fastened  up,  and  the  air  around 
him  compressed,  to  be  afterwards  gradually  let  out. 

The  idea  that  compressed  air  is  liable  to  burst  in  the 
drum  of  the  ear  is  an  erroneous  one.  There  is  a  little 
tube  connecting  the  inside  of  the  ear  with  the  nose,  so 
that  the  pressure  is  the  same  on  both  sides  of  the 
"drum,"  and  consequently  there  is  no  tendency  to 
burst  it  in.  There  is  the  possibility,  it  is  true,  that 
the  tube  may  be  stopped  up  through  some  temporary 
cause,  such  as  a  cold,  but  the  action  of  swallowing  will 
probably  clear  it,  and  if  not,  the  ears  will  hurt  the 
diver  before  he  has  gone  far  down,  and  he  will  return 
to  the  surface. 

There  are  jobs,  however,  in  which  the  necessity  of 
a  tube  for  the  supply  of  air  makes  the  use  of  a  diving 
dress,  such  as  that  just  described,  quite  impracticable. 
In  a  flooded  mine,  for  example,  where  the  diver  may 
have  to  clamber  about  over  obstructions  and  through 
tortuous  passages,  it  would  be  impossible  for  him  to 
drag  a  long  length  of  pipe  after  him.  For  such  cases, 
a  self-contained  apparatus  may  be  used,  in  which  the 
man  takes  his  atmosphere  with  him,  something  like 
the  submarine  escape  apparatus,  described  in  the  last 
chapter. 

It  is  generally  stronger,  however,  and  enables  the 
man  to  live  without  fresh  air  for  a  longer  period — as 
much  as  two  hours.  For  this  purpose  a  small  steel 
cylinder  is  slung  on  his  back,  into  which  is  compressed 

198 


Submarine  Diving 


about  one  hundred  cubic  feet  of  air  with  an  extra 
proportion  of  oxygen  in  it.  He  also  carries  a  metal 
chamber  containing  caustic  soda,  which  absorbs  the 
carbonic  acid  produced  by  breathing.  By  this  means 
the  air  in  the  helmet  can  be  breathed  several  times 
over,  and  at  the  same  time  gradually  replaced  by  fresh 
air  from  the  cylinder. 

Any  of  these  forms  of  diving  dress  can  be  used  in 
rescue  operations  at  fires  or  after  colliery  explosions  ; 
for,  equipped  with  them,  men  can  walk  about  unharmed 
in  the  foulest  atmosphere. 

Another  method  of  diving  is  by  means  of  a  diving- 
bell.  This  is  a  large  steel  box,  open,  as  a  bell  is,  at 
the  bottom,  but  otherwise  completely  air-tight.  The 
men  get  inside  it,  and  the  whole  thing  is  then  lowered 
on  to  the  bed  of  the  sea  or  river.  Of  course,  the  air 
enclosed  in  the  bell  prevents  the  water  from  entering, 
and  they  can  then  work  on  the  sea-floor,  just  as  in  the 
case  of  the  caisson  described  in  the  chapter  on  bridges. 
Indeed,  a  caisson  is  simply  a  special  type  of  diving-bell. 

Of  course,  air  is  pumped  down  into  the  bell  through 
a  pipe,  continually,  and  it  afterwards  escapes  through 
the  open  end  of  the  bell  and  bubbles  up  through  the 
water.  Thus  the  sight  of  air  coming  up  from  below, 
where  diving  operations  are  going  on,  which  usually 
seems  alarming  to  the  uninitiated  onlooker,  is  really  a 
sign  that  all  is  right  and  that  the  men  below  are  being 
given  a  plentiful  supply  of  fresh  air. 

These  " diving-bells"  are  often  used  in  the  building 
of  breakwaters  with  concrete  blocks.  The  bell  is 
lowered  by  a  crane  on  to  the  floor  of  the  sea  just  where 
a  block  is  to  be  laid,  and  the  men  inside  it  can  then 
easily  level  the  ground  and  make  it  ready  to  receive 
the  block.  Then  the  bell  is  drawn  up  and  the  block 
lowered  into  its  place,  being  adjusted  by  "  helmet " 
divers. 

199 


Submarine  Diving 


Sometimes  a  diving-bell  has  a  shaft  and  air-lock 
fitted  to  it,  like  a  caisson,  and  it  is  then  called  a 
<(  caisson  bell."  Men  and  material  may  then  pass  up 
and  down  without  the  necessity  of  raising  the  bell  every 
time.  Which  kind  of  bell  is  used  depends  upon  the 
particular  nature  and  circumstances  of  the  job. 

In  some  cases  a  decompression  chamber  is  fitted 
in  the  upper  part  of  the  bell,  and  when  it  is  time  to 
return  to  the  surface,  the  men  get  into  this  and  seal 
themselves  up.  The  bell  may  then  be  drawn  up  as 
quickly  as  the  crane  can  lift  it,  without  risk  to  the  work- 
men, who  let  the  air  in  the  chamber  escape  gradually 
until  the  pressure  has  all  gone,  when  they  emerge  from 
their  temporary  prison. 

The  British  Admiralty  have,  at  Gibraltar,  a  special 
diving-bell  plant,  for  laying  moorings.  It  consists  of  a 
steam-barge,  with  a  large  hole  in  the  centre,  and  in 
this  hole  there  hangs  a  diving  bell,  suspended  by  wire 
ropes.  When  it  is  desired  to  fix  a  mooring  on  the  bed 
of  the  sea,  this  barge  is  anchored  over  the  spot  and 
the  bell  is  lowered.  When  the  work  is  finished,  the 
bell  is  drawn  up  again,  and  the  barge  moves  away. 

An  interesting,  because  unusual,  example  of  divers' 
work  occurred  not  long  ago  at  Winchester  Cathedral. 

It  is  evident  that  the  builders  of  this  structure,  which 
was  erected  in  the  eleventh  and  thirteenth  centuries, 
encountered  water  when  they  had  dug  down  to  a  depth 
of  about  10  feet,  so  they  were  unable  to  carry  the 
foundations  lower  than  that.  They  therefore  dug 
trenches  of  that  depth,  placed  a  layer  of  timbers  at  the 
bottom,  covered  them  with  chalk,  and  then  proceeded 
to  build  the  walls.  These  foundations  lasted  for  cen- 
turies, but  eventually  subsidences  began  to  occur  which 
endangered  the  safety  of  the  whole  building. 

On  investigation,  it  was  found  that  below  the  water- 
level  there  was  a  bed  of  clay  6  feet  thick,  then  a  peat 

200 


Submarine  Diving 


bog  8  feet  6  inches  thick,  and  then  a  bed  of  gravel,  and 
it  became  apparent  that  if  the  foundations  could  be 
"  underpinned  " — that  is,  fresh  masonry  placed  under- 
neath, until  they  reached  right  down  to  the  gravel — the 
venerable  building  could  be  saved.  At  first  sight  this 
would  seem  a  very  easy  thing  to  do — just  dig  away  the 
earth  from  the  foundations,  a  small  portion  at  a  time, 
and  pump  out  the  water  while  the  men  go  down  and 
do  the  necessary  work  ;  then,  one  little  piece  being 
finished  in  this  manner,  fill  in  the  excavation  and 
repeat  the  process  with  another  small  piece. 

There  is  this  difficulty,  however.  The  action  of 
pumping  would  suck  some  of  the  sandy  and  other  lighter 
material  from  under  the  foundations,  and  so  bring  the 
building  down. 

The  only  hope  of  saving  the  cathedral,  then,  lay  in 
the  employment  of  a  diver. 

First  of  all  the  earth  was  dug  away  from  the  side 
of  the  wall  to  a  width  of  about  5  or  6  feet,  and  to 
the  depth  of  the  old  foundations,  at  which  point  water 
was  reached.  Then  the  diver  took  the  work  in  hand, 
digging  downwards,  and  also  horizontally  under  the 
wall,  until  he  had  removed  all  the  clay  and  peat. 
Then  bags  of  cement  concrete  were  let  down  to  him, 
and  these  he  laid  side  by  side  until  the  whole  area  of 
the  excavation  had  been  covered.  With  a  sharp  knife 
he  then  slit  the  bags  open  and  spread  the  concrete, 
after  which  it  was  left  to  set. 

With  the  layer  of  solid  concrete  at  the  bottom  it  was 
safe  to  pump  the  water  out,  so  that  the  rest  of  the 
work  could  be  done  in  the  dry  in  the  ordinary  way. 

Thus,  in  short  lengths,  a  few  feet  at  a  time,  the 
whole  of  the  walls  were  carried  down  on  to  the  firm 
stratum  of  gravel,  and  the  structure  is  now  safe. 

When  we  remember  that  all  this  work  has  to  be 
done  by  the  diver  in  pitch  darkness  and  entirely  by 

201 


Submarine  Diving 

"feel,"  it  is  impossible  to  withhold  our  admiration  of 
the  men  who  perform  such  tasks. 

It  frequently  happens  that  submarine  rocks  have  to 
be  removed,  in  the  interests  of  the  shipping  to  which 
they  constitute  a  great  danger,  and  here  again  the  diver 
is  essential. 

The  diver,  of  course,  inspects  the  rock  and  decides 
where  the  hole  or  holes  should  be  in  which  the  ex- 
plosive is  to  be  placed.  Then  the  holes  are  bored. 

Sometimes  he  does  this  himself,  with  a  pneumatic 
drill  (see  chapter  on  tools)  supplied  with  compressed 
air  from  the  boat  above.  At  other  times  it  is  done 
with  a  diamond  drill,  worked  by  a  steam-engine  on  a 
barge  anchored  over  the  spot. 

A  diamond  drill  consists  of  a  hollow  steel  bar,  or 
tube,  in  one  end  of  which  are  fixed  a  number  of 
diamonds.  These,  being  the  hardest  substance  known, 
can  cut  through  anything ;  and  so,  when  the  bar  is 
turned  rapidly  round  by  the  steam-engine  above,  it 
quickly  cuts  a  large  circular  hole  in  the  rock. 

When  the  hole  is  ready,  the  diver  clears  it  of  any 
dirt  or  small  pieces  of  rock,  and  right  at  the  very 
bottom  of  it  he  places  the  explosive,  generally  dyna- 
mite. This  is  in  the  form  of  cartridges,  and  after  it  has 
been  put  in  and  carefully  pushed  down,  the  hole  is 
sealed  up  with  clay,  or  something  of  that  sort,  which 
forms  what  is  known  as  the  "  tamping."  Through  the 
tamping  two  insulated  wires  are  led  up  into  the  boat. 
Every  onepiaving  then  withdrawn  to  a  safe  distance,  the 
explosive  is  fired  by  electricity  and  the  rock  is  blown 
to  pieces. 

There  is  another  way  of  breaking  up  a  sunken  rock 
without  the  aid  of  an  explosive.  A  large  bar  of  steel 
is  used,  weighing  perhaps  10  tons,  with  a  point  of  very 
hard  steel,  like  that  of  an  armour-piercing  shell.  This 

202 


Submarine  Diving 


is  suspended  from  a  boat  anchored  over  the  rock,  and 
is  alternately  pulled  up  and  dropped,  care  being  taken 
that  it  shall  always  fall  upon  exactly  the  same  spot. 
Its  action  is  therefore  exactly  like  that  of  the  sharp- 
pointed  hammer  with  which  coal  is  broken  in  the 
domestic  coal-cellar. 


203 


CHAPTER    XVI 

WATER-SUPPLY 

No  work  of  the  engineer  touches  the  welfare  of  the 
public  more  closely  than  the  provision  of  water  for 
domestic  use. 

There  is  no  naturally  pure  water.  The  rain  becomes 
contaminated,  even  as  it  falls,  by  impurities  acquired 
from  the  air  ;  and  no  sooner  has  it  touched  the  ground 
than  it  commences  to  pick  up  still  more. 

These  impurities  are  of  two  kinds.  First  there  are 
substances  dissolved  in  the  water,  just  as  sugar  is  dis- 
solved in  tea,  and  in  that  case  the  particles  of  the 
substance  and  the  particles  of  water  are  so  intimately 
mixed  that  it  is  not  easy  to  separate  them — no  form  of 
filtration  will  do  it.  Fortunately,  however,  these  im- 
purities are  not  of  serious  moment,  producing  merely 
what  is  known  as  "  hardness,"  so  they  are  for  the  most 
part  left  in  the  water  as  it  reaches  us  through  the 
«  main." 

The  other  impurities  are  matters  held  "  in  suspen- 
sion" by  the  water — that  is,  floating  in  it.  Muddy 
water  is  an  example  of  this,  the  dirty  colour  being 
due  to  tiny  solid  particles  "suspended"  in  the  water. 
The  heavier  of  these  particles  will,  if  the  water  be  kept 
still  for  a  time,  settle  to  the  bottom,  but  the  lighter 
ones  will  remain  suspended  for  a  long  while  and  so 
have  to  be  filtered  out. 

Some  of  these  particles  are  so  exceedingly  small  that 
they  are  quite  invisible  to  the  naked  eye,  even  when 

204 


Water-Supply 

present  in  large  numbers,  and  water  may  appear  per- 
fectly clear  and  bright,  yet  be  quite  unfit  to  drink. 
This  applies  to  the  deadliest  impurities  of  all,  the 
microbes,  of  which  there  may  be  myriads  in  apparently 
clean  water,  some  of  them,  perhaps,  capable  of  pro- 
ducing serious  disease. 

It  is  these  matters  "  in  suspension,"  then,  and  parti- 
cularly the  microbes,  against  which  the  water-engineer 
has  to  wage  incessant  war. 

When  we  reflect  upon  this  matter  and  think  of  the 
vast  volume  of  water  which  has  to  be  provided  to 
supply  the  needs  of  a  large  town,  and  the  enormous 
difficulty  of  freeing  it  from  these  insidious  little  foes, 
it  is  surprising  that  we  do  not  have  to  pay  for  it  by 
the  pint  instead  of  having  an  unlimited  supply  of  it 
for  a  water-rate  of  a  few  pounds  or  even  shillings  per 
year. 

After  the  rain  has  fallen  upon  the  earth,  a  certain 
amount  of  it  soaks  in  and  penetrates  to  a  great  depth, 
until  it  reaches  a  waterproof  stratum,  in  a  hollow  of 
which  it  lies,  as  in  a  great  subterranean  reservoir. 
This  water,  in  slowly  percolating  through  the  earth, 
undergoes  a  natural  process  of  filtration,  and  so  if 
we  sink  a  deep  well,  and  tap  the  underground  reservoir, 
we  shall  obtain  a  supply  of  really  excellent  water — not 
by  any  means  pure,  observe,  but  free  from  all  dangerous 
impurities.  The  sides  of  our  well  must  be  waterproof, 
however,  in  order  to  make  it  quite  certain  that  we 
draw  it  all  from  the  bottom,  and  do  not  get,  mixed 
with  it,  any  other  water  which  has  escaped  the  filtering 
process.  For  that  which  is  found  near  the  surface, 
and  in  shallow  wells,  is  of  very  doubtful  quality. 

Deep  wells,  however,  will  not  provide  sufficient  water 
for  a  large  town,  so  that  in  most  cases  recourse  must 
be  had  to  river  water.  The  great  bulk  of  the  supply 
of  London,  for  example,  comes  from  the  Thames  and 

205 


Water-Supply 


the  Lea,  and  when  we  contemplate  the  many  sources 
of  possible  contamination  to  which  the  water  of  such 
rivers  is  liable,  it  seems  truly  remarkable  that  it  can 
ever  be  rendered  fit  for  drinking  at  all.  Fortunately, 
however,  it  can  be  done  by  methods  which  are  very 
simple,  and,  as  is  proved  by  the  excellent  health  enjoyed 
by  those  who  live  in  some  of  the  largest  towns,  per- 
fectly reliable. 

The  reason  for  this  very  satisfactory  state  of  things, 
as  we  shall  see  presently,  is  that  impure  water  contains 
within  itself  the  very  material  which  is  required  to 
purify  it. 

The  foundation  of  the  present  systems  of  treating 
water  was  laid  in  1829  by  Mr.  James  Simpson,  the 
engineer  at  that  time  of  the  Chelsea  Water  Company 
(London).  He  took  raw  water — dirty  water  we  might 
really  call  it,  only  "  raw  "  sounds  less  offensive — from 
the  Thames  and  placed  it  in  tanks  called  *'  decanting 
basins,"  where  it  remained  at  rest  for  a  period ;  exactly 
how  long  he  gave  it  is  not  known,  but  the  present  day 
practice  is  about  twenty-four  hours.  During  this  time  the 
heavier  particles  of  suspended  matter  fall  to  the  bottom, 
and  the  clarified  water  is  then  drawn  off  through  a 
floating  pipe,  so  that  it  is  always  taken  from  near  the 
surface.  Periodically,  of  course,  the  decanting  basins 
are  cleared  of  the  sediment  which  collects  at  the 
bottom. 

Sometimes  the  process  is  assisted  by  the  addition 
of  chemicals,  generally  alum,  which  combines  with 
certain  substances  in  the  water,  and  then  falls  to  the 
bottom,  carrying  with  it  a  good  deal  of  the  suspended 
matter. 

From  the  decanting  basins  he  led  the  water  to 
sand  filters,  and  it  is  a  very  remarkable  fact  that 
although  bacteriology — the  science  which  relates  to 
microbes — was  unknown  in  Mr.Simpson's  day,he  appears 

206 


Water-Supply 

to  have  hit  upon  the  most  perfect  means  of  inter- 
cepting them.  In  other  words,  although  he  could  not 
at  that  time  have  been  aware  of  the  real  nature  of  these 
deadly  "  impurities/'  he  nevertheless  invented  a  form 
of  filter  which  is  still  up-to-date,  and  is  used  now  in 
all  parts  of  the  world. 

It  consists  of  a  large  tank,  in  the  floor  of  which 
channels  are  formed  ;  upon  this  floor  is  laid  a  layer 
of  coarse  gravel,  then  a  layer  of  fine  gravel,  then  coarse 
sand,  and  finally  about  3  feet  of  fine  sand.  It  is  this 
fine  sand,  or  rather  the  top  half-inch  of  it,  which  really 
forms  the  filter.  The  water  flows  in  at  the  top,  and 
very  slowly  percolates  downwards  through  the  sand 
and  gravel,  finally  passing  away  through  the  channels. 
At  first  the  filtration  is  very  imperfect,  and  the  water 
is  allowed  to  run  to  waste  ;  but  it  gradually  improves 
until,  after  about  twenty-four  hours,  the  filter  becomes 
what  is  known  as  "  ripe,"  and  the  water  which  comes 
from  it  is  then  fit  for  drinking. 

Microscopical  examination  shows  that  by  that  time 
the  grains  of  sand  forming  the  top  surface  have  become 
coated  with  a  substance  to  which  the  name  of  "  zooglea 
jelly  "  has  been  given.  It  is  evidently  formed  out  of 
something  contained  in  the  water,  and  it  constitutes 
the  real  filtering  material.  It  effectively  keeps  back 
not  only  microbes  but  other  impurities,  and,  so  long  as 
the  layer  of  jelly-coated  sand  is  not  disturbed,  the  filter 
can  be  relied  upon  to  pass  only  water  fit  for  drinking 
by  human  beings. 

After  a  time,  of  course,  dirt  collects  upon  the  surface 
of  the  filter,  and  then  a  thin  layer  of  sand,  with  the  dirt, 
has  to  be  removed,  but  after  a  day  or  so  the  filter 
"ripens"  again  and  works  as  well  as  before.  If  the 
preliminary  clarification  of  the  water  is  good,  a  filter 
will  work  without  cleaning  for  a  year  or  more. 

In  the  case  of  large  towns  there  are  usually  large 

207 


Water-Supply 


storage  reservoirs.  The  use  of  these  enables  the  water 
to  be  taken  from  the  river  only  when  it  is  comparatively 
clean.  After  heavy  rains,  when  the  river  is  muddy,  no 
water  is  taken.  The  prolonged  storage  also  enables  a 
great  part  of  the  suspended  matter  to  settle,  just  as  it 
does  in  the  decanting  basins.  The  latter  are  still  used, 
however,  in  many  small  towns  where  the  cost  of  a  large 
storage  reservoir  would  be  too  heavy. 

It  might  seem,  from  what  has  been  said,  that  the 
methods  of  purifying  water  have  not  undergone  any 
development  since  Mr.  Simpson's  time,  and,  so  far  as 
the  sand  filter  is  concerned,  that  is  practically  the  case. 
A  French  engineer,  named  Puech,is  responsible,  however, 
for  an  improved  method  of  clarifying  the  water,  which 
is  being  largely  adopted  now  in  place  of  the  decanting 
basins.  It  is  much  more  effective  than  they,  and  so 
enables  the  "  Simpson  "  filters  to  go  for  a  longer  time 
without  needing  to  be  cleaned. 

His  system  consists  of  a  series  of  filters  through 
which  the  "  raw  "  water  is  passed.  First  there  is  one 
entirely  of  coarse  gravel,  then  one  of  finer  gravel,  and 
another  and  another,  and  finally  one  of  coarse  sand, 
making  generally  five  in  all.  Their  action  is  quite 
different  from  the  Simpson  filter,  for  the  dirt  is  deposited 
on  the  gravel  or  sand  right  through  the  whole  layer  and 
not  simply. on  the  surface;  indeed  every  particle  of 
gravel  appears  to  take  its  share  in  the  process,  the 
water  leaving  some  of  its  impurities  on  every  one  that 
it  touches,  just  as  we  know  all  dirty  water  does  on 
any  solid  substance  it  may  happen  to  come  in  con- 
tact with.  The  action  is  so  thorough,  however,  that 
it  leaves  nothing  for  the  Simpson  filter  to  do  except  to 
deal  with  the  microbes. 

Of  course,  such  filters  soon  get  very  dirty,  and 
M.  Puech  has  invented  a  very  ingenious  method  of 
cleaning  them.  In  the  bottom  of  each  filter  there  is  a 

208 


Water-Supply 

series  of  pipes  through  which  air  can  be  blown.  This, 
bubbling  up  through  the  gravel  and  water,  pro- 
duces an  effect  very  similar  to  the  action  of  water  when 
boiling  (only,  of  course,  the  water  is  cold),  and  causes 
the  dirt  to  be  carried  upwards  to  the  surface.  At  the 
same  time  a  current  of  water  is  caused  to  flow  along 
the  surface  and  carry  the  dirt  away.  Thus  a  filter  can 
be  cleaned  in  a  very  short  time. 

Filtered  water  is  kept  in  covered  reservoirs.  These 
are  generally  made  of  brickwork  or  concrete,  with  a 
roof  of  the  same  material  consisting  of  small  arches 
supported  on  piers,  the  whole  structure  much  resembling 
the  vaults  under  a  cathedral.  The  sides  are  made 
watertight  with  a  layer  of  cement,  and  the  roof  with  a 
layer  of  asphalt,  to  prevent  the  possible  contamination 
of  the  water  by  any  soaking  through. 

Reservoirs  for  storing  unfiltered  water  are  generally 
open,  and  to  all  appearance  are  simply  a  piece  of  ground 
enclosed  by  a  mound  of  earth  something  like  a  railway 
embankment.  Many  people  have  wondered  how  ever 
it  comes  about  that  such  a  structure  can  hold  water, 
and  if  it  were  only  what  it  appears  to  be  there  is  no 
doubt  that  the  water  would  soak  into  the  earth  or 
through  the  bank,  as  quickly  as  it  was  pumped  in. 
The  mystery  is  solved,  however,  when  we  know  that 
such  a  reservoir  is  only  built  upon  a  spot  where  there 
is  a  continuous  stratum  of  clay  or  other  waterproof 
material  close  to  the  surface,  and  concealed  in  the 
embankment  there  is  a  vertical  wall,  also  of  clay,  carried 
right  down  into  the  waterproof  stratum  below.  Thus 
it  is  a  complete  tank  of  impervious  material. 

THE  GREAT  COOLGARDIE  WATER  SCHEME 

So  far  we  have  been  dealing  mainly  with  the  methods 
by  which  water  is  cleaned  and  purified.  We  will  now 

209  O 


Water-Supply 


turn  to  an  example  of  the  way  in  which  water  is 
conveyed  from  one  place  to  another. 

In  the  year  1892  gold  was  discovered  in  a  remote 
part  of  Western  Australia,  near  the  present  town  of 
Coolgardie.  The  region  was  dry  and  desolate,  scarcely 
any  water  could  be  obtained,  and  what  little  there  was 
was  salt.  In  those  early  days  water  was  a  luxury, 
costing  half-a-crown  a  gallon,  and  even  then,  as  it  was 
very  impure,  caused  much  sickness. 

As  the  goldfield  developed,  it  became  evident  that 
something  must  be  done,  and  so  the  Colonial  Govern- 
ment decided  upon  a  great  scheme^ 

Among  the  Darling  range  of  mountains,  near  the 
coast,  there  is  a  river  known  as  the  Helena  River,  of 
very  pure  water,  which  flowed  through  a  narrow  valley. 
At  one  point  in  this  valley  two  gigantic  arms  jut  out 
from  the  mountains  on  either  side,  forming  a  narrow 
gate  through  which  the  river  passed.  Such  a  spot  was 
an  almost  ideal  one  for  the  construction  of  a  dam,  and 
accordingly  a  large  concrete  dam  was  built  across  this 
narrow  opening.  The  general  methods  of  building 
such  a  structure  have  been  referred  to  in  an  earlier 
chapter,  so  it  will  be  enough  to  state  here  that  the 
dam  is  760  feet  long,  and  about  100  feet  high  at  the 
deepest  part,  the  foundations  being  carried  dc^vn  nearly 
100  feet  below  the  bed  of  the  river.  At  the  base  it  is 
in  some  parts  120  feet  thick,  tapering  upwards  to  a 
width  of  15  feet  at  the  top. 

The  effect  of  a  dam  like  this  is  to  hold  back  the 
water,  and  form  a  large  lake  or  reservoir,  from  which 
water  can  be  taken  as  required,  while  the  surplus  falls 
over  the  crest  and  flows  on  just  as  it  did  before  the 
dam  was  there.  From  this  reservoir  the  water  is  con- 
veyed through  more  than  300  miles  of  pipes  to  the 
goldfield. 

The  general  lie  of  the  country  rises  from  the  coast 

210 


Water-Supply 

inwards,  and  the  service  reservoir,  which  actually 
supplies  the  town  of  Coolgardie,  is  1200  feet  higher 
than  the  reservoir  formed  by  the  dam  ;  consequently 
the  water  will  not  flow  of  its  own  accord,  but  has  to  be 
pumped.  Eight  pumping  stations,  therefore,  had  to 
be  placed  along  the  route,  each  equipped  with  the 
most  up-to-date  pumping  machinery,  and  it  is  interest- 
ing to  find  that  after  searching  the  world  for  the  best 
machinery,  the  engineers  eventually  gave  the  order  to 
an  Anglo-American  combination,  half  the  engines  being 
made  in  England  and  half  in  the  United  States. 

These  engines  are  worthy  of  a  little  description. 
There  are  twenty  of  them  in  all,  and  they  are  of  the 
kind  known  to  engineers  as  "  horizontal  duplex  triple- 
expansion  direct-acting  Worthington  steam  pumping 
engines."  Each  one  is  practically  two  separate  engines 
(hence  the  term  ^duplex"),  each  of  which  consists 
of  three  steam-cylinders,  and  one  water-cylinder,  or 
pump.  The  steam  passes  through  all  three  cylinders 
in  succession,  thereby  making  full  use  of  the  expansion, 
as  explained  in  an  earlier  chapter,  and  is  then  con- 
densed by  being  brought  into  contact  with  the  cold 
surface  of  the  water-main.  Some  idea  of  the  size  of 
these  engines  will  be  gathered  from  the  fact  that  the 
largest  cylinder  of  each  three  is  nearly  4  feet  in  diameter, 
and  the  stroke  of  the  piston  is  3  feet. 

They  have  no  fly-wheels,  as  the  to-and-fro  motion  of 
the  piston  is  exactly  that  required  to  work  the  pump, 
and  consequently  rotating  parts  are  quite  unnecessary. 
The  piston-rod  communicates  the  movement  of  the 
piston  direct  to  the  plunger  of  the  pump,  which  explains 
the  meaning  of  the  term  "direct-acting."  The  name 
Worthington  refers  to  a  well-known  American  engineer 
who  invented  this  type  of  machine,  and  whose  firm 
actually  made  one-half  of  these  engines. 

The  water-cylinder,  or  pump,  is  not  constructed  in 

211 


Water-Supply 


quite  the  same  way  as  the  cylinder  of  a  steam-engine, 
but  in  principle  it  is  very  similar.  The  plunger  is 
analogous  to  the  piston,  and  as  it  moves  one  way  it  sucks 
water  into  one  end  of  the  cylinder ;  as  it  returns  it 
forces  that  water  out,  and  sucks  a  fresh  lot  in  at  the 
other  end  ;  thus,  whenever  the  plunger  is  moving,  water 
is  being  drawn  in  at  one  end  of  the  cylinder  and  ejected 
at  the  other,  and  the  stream  of  water  produced  is  nearly 
constant.  There  is  a  short  time,  however,  just  as  the 
direction  is  being  reversed,  when  the  plunger  is  still,  and 
so  the  two  halves  of  the  engine  work  alternately,  one 
being  at  the  centre  of  its  stroke  just  as  the  other  is 
starting.  The  flow  of  water  is  thus  very  steady 
— but  it  is  made  more  so  still  by  the  use  of  large 
vessels  containing  air  which  are  connected  to  the 
delivery  pipe  ;  the  air  acts  like  a  spring  cushion  or 
buffer,  and  so  helps  to  keep  the  pressure  in  the  pipes 
quite  steady. 

The  valves  through  which  the  water  enters  and  leaves 
the  cylinder  are  interesting.  They  are,  like  all  pump 
valves,  what  are  known  as  "  non-return  "  valves,  which 
is  to  say  that  they  will  permit  the  water  to  flow  one 
way  but  not  to  go  back  the  other.  The  mushroom 
valves  on  a  gas-engine  are  non-return  valves,  but  those 
used  on  these  engines  are  more  simple  still.  If  we 
picture  to  ourselves  a  hollow  with  a  hole  in  the  bottom, 
and  a  metal  ball  lying  in  the  hollow,  we  shall  get  a  good 
idea  of  what  they  are  like.  Water  entering  through  the 
hole  will  raise  the  ball  and  pass  through  easily,  but  the 
moment  it  tries  to  get  back  the  ball  will  cover  the  hole 
and  effectually  seal  it  up.  The  water  is  drawn  in  through 
a  valve  of  this  description  situated  in  the  bottom  of  the 
cylinder,  and  is  forced  out  through  a  similar  one  placed 
at  the  top. 

The  power  of  each  engine  is  stated  as  300  horse- 
power, but  that  gives  us  little  idea  of  their  great  size  and 

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Water-Supply 


strength,  for  an  engine  engaged  in  moving  a  heavy  and 
inelastic  substance  like  water  has  to  work  very  slowly, 
and  of  course  the  slower  an  engine  moves  the  larger  it 
has  to  be  to  do  a  given  amount  of  work.  A  300  horse- 
power high-speed  engine  would  look  a  mere  pigmy  if 
placed  beside  these  large  machines. 

In  speaking  of  a  pumping  plant  it  is  customary  to 
refer  to  its  "  duty,"  by  which  is  meant  the  amount  of 
work  it  is  capable  of  doing  for  every  pound  of  coal 
burnt,  and  it  is  very  interesting,  as  giving  us  an  idea  of 
the  vast  amount  of  energy  stored  up  in  coal.  During 
tests  these  engines  did  work  equal  to  lifting  nearly 
1,000,000  Ibs.  one  foot  high  for  every  pound  of  coal 
burnt — a  truly  wonderful  feat. 

We  are  all  familiar  with  the  large  cast-iron  pipes 
generally  used  for  water  mains  ;  but  in  this  case  pipes 
of  an  unusual  type  were  employed.  They  are  made  by 
an  Australian  firm,  and  are  well  known  out  there.  Two 
large  steel  plates  are  rolled  out  into  the  form  of  a  semi- 
circle ;  the  edges,  too,  are  "  upset  "  in  a  special  machine, 
that  is,  they  are  swelled  out  so  that  the  plate  becomes 
just  a  little  thicker  along  its  edge  than  it  is  elsewhere. 
Then  two  of  these  plates  are  placed  together,  with  two 
special  steel  "  locking  bars,"  as  they  are  called,  between 
them.  These  bars  have  a  groove  on  each  side,  into 
which  the  edges  of  the  plates  fit,  and  when  all  are 
together  a  hydraulic  press  "  pinches  "  the  sides  of  the 
grooves  together,  so  that  they  firmly  grip  the  "  upset ;; 
edges  of  the  plates.  The  pipes  used  on  this  under- 
taking were  30  inches  in  diameter  and  28  feet  long. 
Most  of  them  were  made  of  plates  J  inch  thick,  but 
some  few,  which  had  to  stand  a  specially  heavy  pressure, 
were  a  shade  thicker.  About  60,000  of  them  were 
used,  weighing  about  75,000  tons. 

The  great  reservoir  on  the  Helena  River,  when  full, 
contains  4,600,000,000  gallons  of  water,  and  the  plant 

213 


Water-Supply 

is  designed  to  convey  it  over  the  330  miles  to  the  gold- 
fields  at  the  rate  of  5,500,000  gallons  per  day. 

WATER  SOFTENING 

We  can  now  leave  the  public  water-works  altogether 
and  consider  a  very  important  process  of  purification 
frequently  carried  on  by  the  consumer  himself. 

Those  of  us  who  live  in  the  country  can,  and  generally 
do,  provide  ourselves  with  a  supply  of  soft  water,  by 
collecting  the  rain  which  falls  upon  the  roofs  of  our 
houses  ;  a  privilege  which  is  denied  the  dweller  in  a 
large  town,  because  the  dirt  which  settles  upon  his  roof 
renders  such  water  quite  unfit  for  use.  Probably  every 
one,  however,  has  experienced  the  luxury  of  a  wash  in 
soft  water,  and  while  he  may  not  know  the  precise 
reason,  he  is  fully  aware  that  there  is  an  important 
difference  between  it  and  the  hard  water  from  the 
"  main."  In  many  industries — such,  for  example,  as 
laundries  and  dye-works — soft  water  is  almost  a  necessity, 
while  everywhere  where  steam  boilers  are  in  use  it  is  a 
great  advantage,  for  hard  water  leaves  a  slaty  deposit 
inside  the  boiler,  which,  if  not  removed  at  great  expense, 
causes  a  great  waste  of  heat,  and  sometimes  even  serious 
accidents. 

The  hardness  of  water  is  due  to  certain  substances, 
principally  forms  of  lime  and  magnesia,  which  it  dis- 
solves out  of  the  earth,  and  which,  as  mentioned  already, 
are  not  removed  by  the  processes  used  at  the  water- 
works. 

When  we  wash  our  hands  in  soft  water  we  find  that 
we  get  them  clean  much  quicker  and  with  less  soap 
than  when  we  use  hard  water.  This  is  because  the 
dirt  upon  our  hands  is  stuck  on  with  grease,  and  to 
get  it  off  we  must  dissolve  that  grease,  just  as  we  must 
dissolve  the  gum  in  order  to  get  a  stamp  off  an 
envelope,  and  grease  will  not  dissolve  in  water  ;  soap, 

214 


Water-Supply 


however,  contains  soda,  which  becomes  mixed  with 
the  water,  and  then  it  is  able  to  dissolve  the  grease. 
But  if  there  is  a  certain  form  of  lime  in  the  water, 
the  soda  prefers  to  combine  with  it  instead,  and  as 
hard  water  contains  this  form  of  lime,  there  is  no  soda 
available  for  washing  until  the  lime  has  taken  up  all 
the  soda  that  it  can  combine  with  ;  in  other  words, 
a  certain  amount  of  time  and  a  considerable  quantity 
of  soap  have  to  be  expended,  before  the  cleaning  of  our 
hands  begins  at  all. 

We  can  get  these  impurities  out  of  the  water  by 
distilling  it — that  is,  evaporating  it  into  steam  and  then 
condensing  it  back  into  water,  but  that  is  too  expensive 
a  process  for  commercial  purposes.  Some  of  them 
can  be  removed  by  boiling  the  water,  being  thrown 
out  of  solution  and  settling  on  the  bottom  and  sides 
of  the  vessel,  and  ultimately  forming  a  stony  deposit, 
such  as  is  often  found  in  domestic  tea-kettles. 

They  can  all  be  removed  cheaply,  however,  by 
means  of  chemicals.  Certain  substances  are  capable 
of  being  dissolved  in  water,  while  others  are  not,  and 
in  some  cases  we  can  turn  a  soluble  substance  into 
an  insoluble  one.  If  to  a  quantity  of  water  with  some 
substance  dissolved  in  it  we  add  some  other  substance, 
which  will  combine  with  the  first,  and  together  with  it 
form  an  insoluble  one,  it  will  then  be  precipitated,  that 
is,  will  separate  itself  from  the  water,  and  either  fall  to 
the  bottom  of  the  vessel  or  submit  to  be  filtered  out. 
This  is  the  principle  upon  which  water  is  softened  by 
chemical  action. 

There  are  several  systems  for  softening  water  on  the 
market,  some  of  them  entirely  depending  upon  the  use 
of  chemicals,  and  some  which  employ  heat  as  well.  A 
whole  book  could  be  written  about  them,  but  a  descrip- 
tion of  one  of  the  best  known  will  be  sufficient. 

Imagine  a  tall  cylindrical  tank,  formed  of  steel  plates 

215 


Water-Supply 


riveted  together,  with  a  small  separate  tank  (called  the 
intermediate  tank)  at  the  top.  From  the  bottom  of  the 
intermediate  tank  a  pipe  depends,  inside  the  large  tank, 
with  an  open  end  near  the  bottom  of  the  latter. 

On  the  top  of  all  is  a  curiously-shaped  tank  called 
the  receiver,  which  is  fixed  so  that  it  can  rock  from  side 
to  side  like  a  see-saw,  and  which  has  a  division  inside 
it,  dividing  it  into  two  compartments,  while  just  over  it 
is  the  end  of  a  pipe  from  which  the  hard  water  runs. 
The  water  falls  into  one  compartment  until  it  is  full, 
and  then  the  receiver  overbalances,  tips  over,  and 
empties  that  compartment  into  the  intermediate  tank 
below,  and  at  the  same  time  brings  the  other  com- 
partment under  the  pipe.  So  it  goes  on  oscillating 
from  side  to  side,  a  definite  quantity  of  water  being 
tipped  into  the  intermediate  tank  at  each  oscillation. 

Close  to  the  receiver  is  another  tank  containing  the 
chemicals,  and  every  time  the  receiver  tips  over,  it 
opens  a  valve  and  lets  a  certain  amount  of  the  liquid 
chemicals  flow  out  of  the  chemical  tank  into  the 
intermediate  tank.  By  this  ingenious  but  perfectly 
simple  contrivance,  just  the  right  proportion  of 
chemicals  is  added  to  the  water,  quite  automatically. 

From  the  intermediate  tank  the  water,  mixed  with 
the  proper  quantity  of  chemicals,  flows  down  the 
vertical  pipe  to  the  bottom  of  the  large  tank.  Up 
this  it  slowly  rises,  the  impurities,  now  rendered  in- 
soluble, falling  to  the  bottom.  At  the  top  of  the  large 
tank  is  a  mass  of  "  wood  wool " — fine  wood  shavings 
— through  which  the  water  passes,  and  then  the  pro- 
cess is  complete.  This  wood  wool  acts  as  a  filter,  and 
intercepts  any  of  the  impurities  which  have  not  already 
been  precipitated,  so  that  only  pure,  soft  water  passes 
out.  A  valve  at  the  bottom  of  the  large  tank  enables 
the  accumulated  deposit  of  impurities  to  be  drawn  off 
periodically. 

216 


CHAPTER   XVII 

ELECTRIC  TRACTION 

ONE  of  the  most  remarkable  changes  that  has  ever 
come  over  public  habits  has  been  brought  about  by 
the  introduction  of  electric  traction. 

Millions  of  people  who  would  rather  walk  or  stay 
at  home  than  travel  in  a  horse  tram  now  go  regularly 
by  electric  car ;  railways  of  a  type  impossible  without 
electricity  now  thrive  on  passengers  who  used  to 
patronise  omnibuses  and  cabs,  while  some  of  the  older 
railways  have  doubled  and  trebled  their  traffic  by 
giving  up  the  steam  locomotive.  Traction  may  there- 
fore be  said  to  be  one  of  the  most  important  of  the 
purposes  to  which  electricity  has  been  applied. 

It  will  be  simpler  if  we  see,  first,  how  electric  power 
is  used  on  tramway  cars,  turning  our  attention  to  the 
electric  railways  later. 

The  electric  equipment  of  a  tramcar  may  be  sum- 
marised as  the  motors,  which  drive  the  car,  the  con- 
trollers and  switches  which  govern  the  supply  of 
current,  the  brakes,  and  the  conductors  which  bring 
the  current  to  the  car. 

The  motors  are  invariably  of  the  direct-current 
variety  described  in  an  earlier  chapter  ;  but  while  they 
are  exactly  the  same  in  principle  as  the  stationary 
motors,  so  often  to  be  seen  driving  machinery,  they 
are  very  different  in  construction.  The  conditions 
under  which  they  work  are  such  that  they  must  be 
of  the  very  highest  class,  both  as  to  material  and 

217 


Electric  Traction 

workmanship.  The  jolting  of  the  car  subjects  them 
to  mechanical  shock  such  as  no  stationary  motor  ever 
has  to  withstand;  while  the  sudden  starting  and  stop- 
ping, and  the  continually  varying  current,  causes  both 
mechanical  and  electrical  stresses,  which  would  soon 
destroy  an  ill-made  machine. 

They  have,  too,  to  be  both  water  and  dirt-proof,  for, 
being  fixed  under  the  car,  they  get  covered  with  dust 
in  dry  weather  and  mud  in  wet.  The  steel  or  iron 
ring  which  constitutes  the  field  magnets  in  an  ordinary 
motor  is  therefore  developed,  in  the  case  of  a  tramway 
motor,  into  a  case  which  completely  encloses  the 
armature  and  through  the  ends  of  which  the  shaft 
projects. 

A  motor  of  a  suitable  size  for  fixing  underneath 
a  tramcar  would  not  be  able  to  develop  sufficient 
power  if  its  speed  were  so  slow  as  to  permit  its  being 
directly  connected  to  the  wheels,  so  there  is  usually 
a  pinion  or  small  tooth-wheel  on  the  motor  shaft  which 
works  into  a  larger  tooth-wheel  on  the  axle  of  the  car, 
which  of  course  increases  the  turning  power,  but 
reduces  the  speed. 

There  are  sometimes  two  and  sometimes  four  motors 
on  a  car,  yet  they  are  all  completely  controlled  by  the 
movement  of  that  one  small  handle  which  the  driver 
moves  from  his  position  in  the  front  of  the  car.  That 
handle  forms  a  part  of  a  very  complex  arrangement 
called  the  "  controller,"  which  is  enclosed  in  the  sheet- 
iron  box  behind  which  the  driver  stands. 

If  we  are  filling  the  domestic  bath  and  the  water  is 
coming  in  too  quickly  we  turn  the  handle  of  the  tap. 
That  has  the  effect  of  partly  closing  the  orifice  through 
which  the  water  passes,  in  that  way  resisting  the  flow 
somewhat,  and  causing  the  water  to  pass  more  slowly. 
In  the  same  way  the  flow  of  electricity  can  be  regulated 
by  placing  a  variable  resistance  in  its  path.  At  some 

218 


Electric  Traction 

convenient  place  upon  the  car,  very  often  under  the 
seat,  there  are  coils  of  wire  which  form  "  resistances/' 
and  these  are  connected  by  a  number  of  wires  to  the 
controller. 

In  the  controller  there  is  a  vertical  shaft  or  drum 
which  is  rotated  by  the  handle,  and  to  which  are  fixed 
a  number  of  copper  segments.  Close  to  these,  but  not 
under  normal  conditions  touching  them,  are  a  number 
of  metal  fingers  which  are  connected  electrically  in 
various  ways — some  to  the  source  of  supply,  some  to  the 
resistance  coils,  some  to  different  parts  of  the  motors, 
and  to  the  brake  magnets  where  a  magnetic  brake  is 
used.  The  arrangement  of  these  segments  and  fingers, 
and  the  way  they  are  connected  up,  is  most  complicated, 
but  when  once  it  has  been  made,  the  operation  of  the 
controller  is  simplicity  itself.  With  the  handle  in  its 
central  position  the  segment  fingers  are  all  separated 
and  no  current  can  pass,  but  as  soon  as  it  is  turned 
slightly  in  one  direction  a  segment  makes  contact  with 
certain  fingers,  forming  a  path  through  which  current 
can  flow  to  the  motors — a  path,  however,  which  offers 
great  resistance,  so  that  that  position  of  the  handle  is 
like  a  tap  partially  turned  on.  As  the  handle  is  turned 
further,  other  segments  and  fingers  come  into  contact, 
with  the  result  that  easier  paths  are  provided  for  the 
current,  until,  in  its  extreme  position,  it  is  like  a  fully 
open  tap  and  the  whole  force  of  the  current  may  pass, 
without  check,  to  the  motor%. 

If  the  handle  is  turned  in  the  opposite  direction,  the 
current  is  kept  shut  off  from  the  motors,  and  the 
magnetic  brake  is  applied  with  varying  degrees  of  force  ; 
the  means  by  which  it  is  brought  about  being  exactly 
the  same,  certain  segments  making  or  unmaking 
contact,  as  the  drum  is  rotated. 

To  one  side  of  the  first  drum  (the  controlling  drum, 
as  it  is  termed),  and  parallel  with  it,  there  is  a  second 

219 


Electric  Traction 

one;  called  the  reversing  drum.  It  is  constructed  in  much 
the  same  way  as  the  other,  and  when  it  is  turned  round 
it  reverses  the  course  of  the  current  through  the  field 
magnets  of  the  motors  and  so  reverses  their  direction. 

The  reason  why  the  current  must  be  tl  turned  on  "  to 
the  motors  gradually  needs,  perhaps,  a  little  explanation. 
As  stated  in  an  earlier  chapter,  the  electric  motor  is  self- 
regulating  as  far  as  the  current  which  it  consumes  is 
concerned.  That  is  because  whenever  the  armature  is 
being  turned  round  an  electric  force  is  generated  in 
it — in  other  words,  it  acts  as  a  dynamo  even  while  it  is 
working  as  a  motor — and  the  force  which  it  generates 
opposes  the  incoming  current.  It  does  not,  it  must  be 
understood,  generate  current,  only  force,  but  that  force 
would  produce  a  flow  of  current  were  it  not  overcome 
by  the  greater  force  of  the  incoming  current,  just  as 
the  current  of  a  sluggish  river  is  overpowered  and 
pushed  back  by  the  greater  force  of  the  rising  tide. 
The  quantity  of  current  which  is  able,  then,  to  pass 
through  a  motor  is  that  due  to  the  number  of  volts  by 
which  the  force  of  the  incoming  current  exceeds  the 
force  generated  in  the  motor  itself.  Now  the  latter  is 
in  proportion  to  the  speed,  so  it  is  easy  to  see  that  when 
the  armature  is  (as  it  is  at  starting)  nearly  still,  there 
is  practically  none  of  the  opposing  force,  so  the  full 
force  of  the  supply  is  available  to  drive  current  through 
the  machine.  This,  if  resistance  were  not  introduced 
artificially,  would  mean  that  at  starting  an  excessively 
heavy  current  would  pass,  heating  the  wires  and  burn- 
ing the  insulating  material — "  burning  out  the  armature/' 
to  use  the  technical  term.  On  the  other  hand,  when 
the  motor  is  working  at  a  good  speed,  it  is  generating 
a  powerful  force  within  itself,  so  that  the  whole  force 
of  the  supply  may  safely  be  used — indeed  is  needed  in 
order  to  force  sufficient  current  through  the  machine 
to  keep  the  speed  up,  if  it  is  doing  hard  work. 

220 


Electric  Traction 

What  has  just  been  described  applies  to  all  motors, 
not  simply  to  those  used  for  traction  purposes,  and  it 
clearly  explains  that  valuable  quality  of  the  electric 
motor  referred  to  previously,  in  virtue  of  which  it  takes 
only  just  as  much  current  as  will  enable  it  to  do  its 
work.  For  we  can  easily  see  that  if  the  "  load  "  on  the 
machine,  or  the  amount  of  work  that  it  is  set  to  do,  be 
increased,  it  will  slow  down  slightly;  the  "opposing" 
force  which  it  generates  will  thereby  be  reduced,  and 
the  quantity  of  current  taken  will  increase,  enabling  it 
to  exert  more  power  to  cope  with  the  increased  work. 
On  the  other  hand,  if  the  load  be  reduced,  the  speed 
increases,  generating  a  greater  "  opposing "  force,  and 
so  automatically  reducing  the  quantity  of  current 
taken. 

In  addition  to  the  controller  there  are,  at  some  con- 
venient place  upon  the  car,  "  fuses " — pieces  of  wire 
which  melt  and  disconnect  the  circuit  if  the  amount  of 
current  coming  into  the  car  exceeds  what  has  been 
decided  upon  as  the  safe  limit.  There  is  also,  as  a 
further  precaution,  an  automatic  switch  called  a  "  cut- 
out," generally  placed  under  the  canopy  just  above  the 
driver's  head,  which  opens  and  cuts  off  the  current  if 
it  should  exceed  the  pre-determined  limit.  It  is  simply 
a  switch  which  is  pulled  open  by  a  spring,  but  which, 
when  closed,  is  held  so  by  a  catch.  There  is  a  small 
electro-magnet  near,  consisting  of  a  few  turns  of  thick 
wire  through  which  the  whole  current  entering  the  car 
passes,  and  of  course  the  strength  of  that  magnet  varies 
with  the  amount  of  current  flowing  in  the  coil.  As 
soon  as  the  current  reaches  a  certain  volume,  the  mag- 
net becomes  strong  enough  to  release  the  catch,  where- 
upon the  switch,  under  the  influence  of  the  spring, 
flies  open,  and  cuts  off  the  current. 

Regular  travellers  by  electric  car  must  all,  at  some 
time,  have  been  startled  by  a  loud  "  click,"  accompanied 

221 


Electric  Traction 

by  a  flash  of  light,  coming  from  somewhere  over  the 
driver's  platform.  That  is  the  "  cut-out "  operating. 
It  will  be  found  to  occur  generally  when  the  car  is 
starting  under  a  heavy  load,  perhaps  uphill.  The 
driver  moves  his  handle  a  little  too  fast,  "  turning  on  " 
the  current  more  quickly  than  the  motor  gets  up  its 
speed,  so  that  too  heavy  a  current  passes.  As  the 
writer  once  had  occasion  to  explain  to  a  nervous 
fellow-passenger,  it  is,  though  startling  because  of  its 
suddenness,  nothing  to  be  alarmed  about,  but  rather 
the  contrary,  for  it  shows  that  this  important  safety 
appliance  is  in  order  and  doing  its  work. 

The  arrangements  for  applying  the  brakes  on  a  tram- 
car  vary  greatly  according  to  the  local  circumstances. 
In  some  cases  a  hand  brake  is  relied  upon,  but  that 
makes  great  demands  upon  the  driver's  physical  strength, 
and  also,  to  a  greater  extent  than  one  would  think,  upon 
his  judgment  ;  for  the  moment  when  the  brakes  are 
doing  the  most  work  is  just  before  the  wheels  begin  to 
skid  on  the  rails,  so  that  to  get  the  best  result  the  driver 
must  put  them  on  hard,  but  must  stop  just  short  of  the 
point  at  which  the  wheels  will  cease  to  revolve — a 
matter  of  no  little  difficulty. 

On  most  systems,  therefore,  there  is  some  kind  of 
electrically  operated  brakes  in  use.  The  simplest  of 
these  methods  is  to  use  the  motors  themselves. 

As  was  remarked  just  now,  a  motor,  even  when 
working  as  a  motor,  behaves  as  a  dynamo  as  well.  In 
the  same  way,  a  dynamo  also  acts,  simultaneously,  as  a 
motor. 

Many  people  suppose  that  the  force  required  to  drive 
a  dynamo,  is  simply  that. necessary  to  overcome  the 
friction  in  the  revolving  part,  as  is,  in  fact,  the  case 
with  most  other  machines.  This  is  only  true  of  a 
dynamo,  however,  so  long  as  no  current  is  taken  from 
it.  As  soon  as  the  two  wires  leading  from  the  dynamo 

222 


Electric  Traction 

are  connected  so  that  current  can  pass,  greater  power 
is  required  to  drive  the  machine.  That  is  because  of 
the  tl  motor-like "  action  within  the  dynamo.  The 
current  which  is  being  generated,  as  it  flows  through 
the  coils,  sets  up  exactly  those  magnetic  forces  which 
we  saw  in  an  earlier  chapter  cause  the  armature  of  a 
motor  to  turn  round,  and  these  magnetic  forces  tend 
to  turn  the  armature  in  the  opposite  direction  to  the 
force  of  the  engine  or  whatever  it  may  be  that  is  driving 
the  dynamo.  Indeed,  by  far  the  greater  part  of  the 
power  employed  to  work  a  dynamo  is  expended  in 
overcoming  these  magnetic  forces,  so  that,  roughly 
speaking,  we  may  say  that  the  power  required  to  drive 
a  dynamo  is  in  proportion  to  the  quantity  of  current 
which  we  take  from  it.  From  that  we  shall  be  able 
to  see  how  the  motors  can  be  utilised  in  "  braking " 
a  tramcar. 

Suppose  the  car  is  running  down  a  hill.  No  current 
is  being  supplied  to  the  motors,  but  they  are  being 
driven  by  the  car,  and  so  are  acting  for  the  time  being 
as  dynamos.  So  long  as  the  wires  leading  from  them 
are  disconnected,  the  driving  of  the  motors  does  not 
absorb  much  of  the  momentum  of  the  car,  but  if  they 
be  connected  through  some  of  the  resistance  coils,  and 
so  a  little  current  taken  from  them,  they  commence 
to  act  as  a  brake.  If  the  resistance  be  gradually  cut  out 
this  braking  effect  will  increase,  until,  if  all  the  resistance 
be  taken  out  of  the  circuit  and  a  heavy  current  allowed 
to  flow  from  the  motors,  the  effect  of  a  very  powerful 
brake  is  obtained.  These  different  connections  are  of 
course  made  and  varied  by  the  simple  movement  of 
the  controller  handle. 

In  some  cases  an  arrangement  is  adopted  known  as 
"  regenerative  control."  In  this,  the  current  generated 
by  the  motors  on  a  car  running  downhill  is  paid  back 
to  the  supply,  so  that  cars  running  down  are  actually 

223 


Electric  Traction 

helping  to  drive  other  cars  which  are  climbing  uphill 
on  other  parts  of  the  system. 

One  of  the  great  electrical  manufacturing  companies 
recently  published  an  illustration  of  what  they  humor- 
ously described  as  the  "  First  example  of  a  Regenerative 
System."  It  consisted  of  a  small  tramway  line  with 
one  car,  worked  by  a  horse.  After  pulling  the  car  up- 
hill, the  horse  got  on  the  car,  which  was  allowed  to  run 
down  by  itself,  under  the  influence  of  gravity  alone. 
By  consuming  a  certain  amount  of  fodder  while  on  the 
downward  journey  the  horse  generated  sufficient  energy 
to  pull  the  car  up  again.  It  does  not  appear  to  be  a 
very  perfect  illustration  of  the  regenerative  principle,  but 
it  is  a  sufficiently  curious  example  of  tramway  working 
to  merit  a  passing  reference. 

A  more  usual  arrangement  is  to  use  the  current 
generated  by  the  motors  to  work  magnetic  track 
brakes.  An  electro-magnet  is  suspended  by  a  spring 
just  above  the  rail,  so  that  normally  it  hangs  quite 
clear.  As  soon,  however,  as  it  is  energised  by  the 
current  it  is  pulled  down  and  grips  the  rail.  The 
friction  between  the  magnet  and  the  rail  causes  the 
former  to  be  pulled  back  relatively  to  the  car,  an  action 
which  is  made  to  pull  a  lever,  and  so  apply  a  brake  to 
the  wheels  just  as  it  is  applied  when  hand-power  is 
used.  There  is  thus  a  threefold  action  ;  first,  the 
check  on  the  motors,  through  current  being  taken  from 
them  ;  then  the  dragging  of  the  magnets  on  the  rails  ; 
and  finally,  the  pressure  of  the  brake-blocks  upon  the 
wheels.  It  will  be  observed  that  as  the  wheels  slow 
down  the  power  of  this  brake  diminishes,  so  that, 
unlike  the  hand-brake,  it  is  impossible  to  apply  it 
too  hard. 

Now  we  come  to  the  means  by  which  the  power  is 
conveyed  from  the  generating  station  or  sub-station  to 
the  cars. 

224 


Electric  Traction 

The  commonest  method  of  all  is  what  is  known  as 
the  trolley  system. 

In  this  there  is  overhead  a  bare  copper  wire,  called 
the  "trolley  wire,"  supported  either  by  long  iron 
brackets,  or  by  wires  spanning  the  street.  This  is  fed 
with  current,  at  intervals  of  about  half  a  mile,  from 
underground  cables.  The  cast-iron  boxes,  or  cup- 
boards, to  be  seen  at  the  side  of  the  road  along  a 
tramway  route,  are  at  the  places  where  the  trolley 
wire  is  thus  fed  with  current.  They  contain  switches 
by  which  the  current  can  be  cut  off  from  the  overhead 
wires  if  necessary. 

In  some  places  there  are  other  wires  stretched  imme- 
diately over  the  trolley  wires.  These  are  called  "guard 
wires,"  and  their  purpose  is  to  prevent  anything,  such  as 
telegraph  wires,  from  falling  upon  the  trolley  wires. 

There  are  generally  automatic  devices  which  cut  off 
the  current  instantly  in  the  event  of  a  trolley  wire 
breaking,  so  that  passengers  in  the  street  below  stand 
no  chance  of  receiving  a  shock. 

The  current  is  conveyed  from  the  trolley  wire  to  the 
car  by  the  trolley  arm,  a  long,  flexible  arm  of  iron, 
which  is  fixed  to  the  roof  of  the  car,  and  carries,  at  its 
upper  end,  a  little  grooved  roller,  called  the  "trolley 
wheel,"  which  runs  along  as  the  car  moves,  in  contact 
with  the  trolley  wire. 

The  wire  which  actually  carries  the  current  from  the 
trolley  wheel  to  the  car  is  well  insulated,  and  is  inside 
the  trolley  arm,  so  that  there  is  little  fear  of  passengers 
on  the  top  of  a  car,  even  if  they  be  touching  the  trolley 
arm,  getting  "  electrified  " ;  but,  as  a  precaution,  the  arm 
itself  is  connected  by  a  good  conductor  to  the  wheels 
of  the  car,  so  that  if,  by  a  remote  chance,  current 
should  escape  from  the  wire  to  the  arm,  it  would 
choose  the  easiest  path  to  the  earth,  through  the 
wheels,  and  notjnjure  any  one. 

225  p 


Electric  Traction 

Another  system,  which  has  been  adopted  very  largely 
— indeed,  almost  exclusively — in  London,  is  the  conduit 
system.  It  is  more  costly  than  the  trolley  system  to 
lay  down,  but  it  has  the  great  advantage,  in  busy  parts, 
that  it  needs  no  posts  to  cause  an  obstruction  to  the 
traffic,  and  no  overhead  wires,  which,  at  junctions 
particularly,  are  somewhat  unsightly. 

It  consists  of  a  small  tunnel,  formed  mainly  of  con- 
crete, under  the  ground,  between  each  pair  of  rails. 
In  the  crown  of  the  tunnel,  or  conduit,  as  it  is  called, 
there  is  a  slot  about  three-quarters  of  an  inch  wide,  and 
within  the  conduit  itself  two  steel  "  conductor  "  rails. 

A  contrivance  called  a  "  plough  "  is  fixed  under  the 
car.  It  has  a  narrow  shank,  thin  enough  to  slide  easily 
in  the  slot,  and  at  its  lower  end  are  two  little  cast-iron 
blocks,  called  "  shoes,"  which  slide  along  in  contact 
with  the  conductor  rails.  The  current  comes  along 
one  of  these  rails,  passes  into  one  shoe,  and  up  through 
a  copper  strip  buried  in  the  shank,  to  the  car.  Thence 
it  returns  via  another  copper  strip  and  shoe  to  the 
other  rail. 

Another  system  is  known  as  the  "  surface-contact  " 
system,  because  the  car  carries  a  shoe  which  makes 
contact  with  objects  let  into  the  surface  of  the  road. 
There  are  several  varieties  of  this  system,  the  idea  of 
which  is  to  secure  the  advantages  of  the  conduit  system 
as  described  just  now,  at  a  less  cost. 

The  chief  difficulty  lies  in  devising  a  suitable  auto- 
matic switch  which  shall  make  each  lt  stud,"  as  it  is 
generally  called  (the  iron  block  in  the  surface  of  the 
road),  "  alive  "  with  current  when  a  car  is  passing  over 
it,  but  "  dead "  as  soon  as  the  car  has  passed.  In 
most  cases  this  is  worked  by  the  action  of  a  powerful 
magnet  on  the  car. 

It  cannot  be  said  that  any  of  the  varieties  of  the 
surface-contact  system  have  "  caught  on,"  up  to  the 

226 


Electric  Traction 

present,  although  examples  are  working  satisfactorily  in 
several  places.  This  is  probably  due  to  the  fact  that, 
considering  the  wear  and  tear  to  the  studs  from  heavy 
vehicles  passing  over  them,  and  the  apparent  liability  to 
damage  through  damp,  people  cannot  bring  themselves 
to  trust  in  the  efficiency  and  reliability  of  the  little 
subterranean  switch,  while  the  consequences  of  people 
stepping  upon  a  stud  accidentally  left  "  alive  "  assume 
more  serious  proportions  in  the  public  mind  than  is 
perhaps  justified. 

Except  in  the  case  of  the  conduit  system,  the 
current,  after  it  has  been  through  the  motors,  is  led  to 
the  wheels,  and  from  them  passes  to  the  rails.  In  order 
to  induce  it  to  flow  along  the  rails  direct  back  to  the 
generating  stations  and  not  to  flow  into  the  earth,  and 
at  the  same  time  to  make  the  track  perfectly  even,  the 
lengths  of  rail  are  generally  welded  together.  Being 
buried  in  the  ground  keeps  the  temperature  of  the  rails 
so  even  that  there  is  no  appreciable  expansion  and 
contraction,  so  that  in  some  cases  the  rails,  after  being 
welded,  are  absolutely  continuous  for  miles.  This  is 
the  more  surprising  because  railway  rails,  which  are 
only  a  few  inches  above  the  surface,  expand  and 
contract  to  such  an  extent  that  a  space  is  left  at  every 
joint,  and  the  bolts  which  connect  them  are  in  oval 
holes,  in  order  that  these  forces  may  have  freedom  to 
expend  themselves,  and  even  then,  in  very  hot  weather, 
they  have  been  known  to  become  bent  through  the 
expansion. 

The  most  usual  way  of  doing  this  welding  is  by 
means  of  a  compound  called  "  thermit."  This  con- 
sists of  a  powder — a  mixture  of  powdered  aluminium 
and  iron  oxide.  If  a  quantity  of  this  mixture  be  placed 
in  a  crucible  and  ignited  at  one  spot,  a  process  of 
combustion  is  started  which,  in  a  few  seconds,  spreads 
throughout  the  whole  mass. 

227 


Electric  Traction 

What  happens  is  this.  The  aluminium  and  the 
oxygen  in  the  iron  oxide  combine,  and  form  what  is 
known  as  "  slag,"  the  iron  out  of  the  oxide  being  left, 
and  great  heat  being  liberated  in  the  process.  Thus, 
after  the  combustion  has  taken  place,  the  crucible 
contains  very  hot  molten  iron  with  a  layer  of  slag 
floating  upon  it.  The  iron  is  not  quite  pure,  but 
contains  a  small  percentage  of  carbon,  so  that  it  is 
about  like  "  mild  steel,"  while  the  heat  produced  by 
the  process  is  so  great  (about  5,400°  Fahrenheit)  that  it 
is  very  fluid. 

In  applying  this  to  the  welding  of  tramway  rails,  the 
two  lengths  to  be  joined  are  placed  end  to  end,  with  a 
small  space,  about  half  an  inch,  between  them.  Then 
the  joint  is  enclosed  in  a  mould  made  of  sand,  formed 
in  two  moulding-boxes,  as  described  in  an  earlier 
chapter,  the  mould  completely  enveloping  the  ends  of 
the  two  rails,  and  forming  a  cavity  into  which  the 
liquid  steel  can  be  poured. 

Then  through  a  hole  in  the  mould  left  for  the 
purpose,  a  gas  (t  torch "  is  introduced,  by  which  the 
ends  of  the  rails  are  made  red  hot. 

Meanwhile,  over  a  hole  in  the  top  of  the  mould  a 
crucible  has  been  fixed,  with  an  iron  plug  in  the 
bottom.  A  quantity  of  thermit  is  then  put  into  this 
and  ignited.  After  about  thirty  seconds  the  combustion 
is  complete,  and  then  the  plug  is  knocked  out  with  an 
iron  bar  and  the  metal  runs  into  the  mould,  completely 
filling  the  space  between  the  two  rails,  absolutely 
uniting  with  them,  and  forming  a  perfectly  homo- 
geneous joint.  The  mould  is  so  shaped  that,  in  addition 
to  filling  the  space  between  the  rails,  the  metal  also 
forms  a  broad,  thick  rib  all  round  the  joint,  just  as 
nature  does  round  the  joint  in  a  once-broken  bone, 
making  the  joint  very  strong. 

The  same  method  of  welding  can,  of  course,  be  used 

228 


Electric  Traction 

for  jointing  other  things  than  tram-rails.  Such  things 
as  propeller  shafts  on  board  ships,  and  large  pieces  of 
machinery  which  have  got  cracked  or  broken,  are 
frequently  mended  very  successfully  by  this  method. 

We  can  now  leave  tramways,  and  turn  our  attention 
to  electricity  as  applied  to  the  hauling  of  railway  trains. 

At  the  commencement,  the  practice  with  regard 
to  electric  railways  was  almost  identical  with  that 
adopted  in  regard  to  tramways.  Direct-current  motors 
were  used,  and  were  supplied  with  current  at  about 
500  volts  (the  usual  voltage  on  tramways),  the  only 
difference  being  that  the  conductor,  instead  of  being  a 
wire  suspended  overhead,  was  a  third  rail,  supported 
upon  earthenware  insulators,  between  the  rails  on  which 
the  wheels  run. 

In  many  cases,  only  one  "  conductor  rail "  was  laid, 
the  electricity,  after  it  had  passed  through  the  motors, 
being  led  to  the  wheels,  thence  finding  its  way  back 
along  the  rails  or  through  the  earth,  as  in  the  case 
of  tramways.  On  some  systems,  however,  there  are 
two  insulated  rails,  one  to  convey  the  current  to  the 
motors  and  the  other  to  take  it  back  again.  On  the 
"  District  "  Railway  of  London  and  most  of  the  London 
tubes  there  are  two  insulated  rails,  while  on  the  City 
and  South  London  Railway  (the  prototype  of  all  the 
tubes)  there  is  only  one,  and  the  writer  has  often 
heard  observant  passengers  remark  upon  this  fact, 
and  speculate  as  to  the  reason  for  the  extra  rail.  It 
may,  therefore,  be  worth  a  short  explanation. 

A  general  idea  seems  to  be  that  it  is  intended  to 
preserve  the  electricity  and  use  it  over  again,  as  if 
electricity  were  a  thing  of  value  which  it  is  wasteful 
to  lose.  This  is  a  complete  misunderstanding  of 
the  very  nature  of  electrical  energy.  It  used  to  be 
the  custom  to  talk  about  the  "electric  fluid,"  and 

229 


Electric  Traction 

although  we  do  not  now  believe  that  electricity  is 
a  fluid,  it  certainly  behaves  in  many  ways  as  if  it 
were,  and  it  is  therefore  often  convenient  to  talk  about 
it  and  think  of  it  as  if  it  were.  We  shall  not  be  far 
wrong,  therefore,  if  we  think  of  the  whole  earth  as 
being  pervaded,  through  and  through,  with  an  invisible 
fluid,  limitless  in  quantity,  and  therefore  of  no  more 
intrinsic  value  than  the  atmosphere  or  the  water  of  the 
ocean,  but  which  we  can  force  along  suitable  conductors 
just  as  we  can  pump  air  or  water  through  a  pipe. 

Just  before  people  began  to  realise  the  possibilities 
of  electricity  as  a  motive-power,  there  were  established, 
in  several  of  the  large  manufacturing  towns,  systems  of 
pipes  by  which  compressed  air  was  supplied  from  a 
central  compressing  station  to  any  manufacturers  who 
cared  to  use  it  as  the  motive-power  to  drive  their  works. 

Now  so  long  as  the  air  was  free,  it  was  of  no 
intrinsic  value,  but  as  soon  as  it  had  been  compressed 
by  the  action  of  the  pumps  it  became  of  value,  and  the 
manufacturers  were  prepared  to  pay  for  it.  When, 
however,  it  had  passed  through  a  compressed-air  motor, 
and  exhausted  its  force  by  working  the  machinery,  it 
became  of  no  value  again. 

In  other  words,  it  was  the  force  which  had  been 
imparted  to  the  air  which  was  of  value,  and  not  the  air 
itself ;  and  in  precisely  the  same  way,  it  is  the  force 
which  the  dynamo  imparts  to  electricity  which  is  of 
value,  and  not  the  electricity  itself.  For  we  may  think 
of  a  dynamo  as  a  pump  which  pumps  electricity  along 
a  conductor  just  as  an  air-compressor  pumps  air  along 
a  pipe.  Therefore,  when  electricity  has  exhausted  its 
force  in  working  a  motor,  it  has  ceased  to  have  any 
value,  and  as  far  as  the  question  of  economy  is  con- 
cerned may  be  discharged  to  the  earth  at  once. 

Suppose,  then,  we  lead  it  to  the  track  rails  ;  some 
of  it  will  flow  along  to  the  point  where  the  other  end 

230 


Electric  Traction 

of  the  dynamo  is  connected  to  the  track  rail,  but  since 
it  is  uninsulated,  some  of  it  will  escape  into  the  earth, 
and  there  form  currents  and  eddies  just  like  what  we 
see  if  we  empty  a  bucketful  of  water  into  a  pond. 
These  currents  and  eddies  will  cause  currents  to  flow 
along  gas  and  water  pipes,  or  any  other  good  con- 
ductors which  may  be  buried  in  the  ground,  thereby 
setting  up  a  process  called  "  electrolysis,"  and  ultimately 
damaging  them.  It  is  to  avoid  this  that  the  second 
insulated  rail  is  used. 

This  brings  us  to  another  little  misunderstanding 
which  it  will  perhaps  be  well  to  clear  up.  When  the 
earth  forms  part  of  an  electric  circuit,  one  end  of  the 
dynamo  or  battery  is  connected  to  the  conductor  and 
one  to  the  earth.  The  current  then  flows  along  the 
conductor  to  the  machine  or  instrument  which  it  has 
to  work,  after  which  it  is  led  to  the  earth,  and  we  speak 
of  it  as  returning  through  the  earth  to  the  battery  or 
dynamo.  Now  in  some  cases,  such  as  telegraphs,  the 
point  where  the  current  enters  the  earth  may  be 
hundreds  of  miles  from  the  point  where  the  dynamo 
or  battery  is  "  earthed  "  ;  how,  then,  can  the  electricity 
find  its  way  back,  all  that  distance,  to  the  right  place  ? 
The  answer  is  that  it  does  not. 

What  happens  can  be  illustrated  by  the  compressed- 
air  installation  referred  to  just  now.  The  compressor 
drew  air  from  the  atmosphere  and  drove  it  along  pipes, 
at  the  end  of  which  it  was  discharged  to  the  atmosphere 
once  more.  There  was  a  complete  air  circuit,  yet  the 
same  air  did  not  travel  round  over  and  over  again. 
Air  was  simply  taken  from  the  great  reservoir,  the 
atmosphere,  at  one  place  and  put  back  at  another.  It 
would  be  impossible  to  detect  it,  but  theoretically  there 
must  have  been  a  movement  of  the  atmosphere  from 
the  point  where  the  air  was  being  discharged  into  it, 
towards  the  place  where  the  compressor  was  sucking 

231 


Electric  Traction 

air  out  of  it.  That  exactly  illustrates  what  happens 
when  a  dynamo  or  battery  draws  electricity  from  the 
earth  at  one  point,  which  is  discharged  back  to  the 
earth  at  a  distance — a  slight  general  movement  of  the 
electricity  in  the  earth  from  the  one  point  to  the 
other. 

As  has  been  stated  above,  the  early  electric  railways 
were  constructed  and  worked  precisely  on  the  same 
lines  as  electric  tramways,  but  in  recent  years  the 
electrical  equipment  of  railways  has  developed  along 
lines  of  its  own. 

We  saw  in  the  chapter  on  the  "Transmission  of 
Power,"  that  for  reasons  of  economy,  when  great  power 
has  to  be  transmitted  over  a  long  distance  by  electricity, 
the  current  has  to  be  at  a  high  voltage,  and  also  of  the 
alternating  variety.  On  the  tramways  and  early  rail- 
ways this  current  is  transformed,  and  converted  in 
sub-stations  into  low  voltage  direct  current  for  use  on 
the  cars  and  trains. 

Now  these  sub-stations  are  costly  to  build  and  to 
maintain,  so  the  idea  gradually  developed  that  it  would 
be  a  good  thing  if  they  could  be  dispensed  with  alto- 
gether. For  tramways  it  is  obviously  impossible,  for 
high-tension  currents  flowing  along  bare  conductors  in 
the  public  streets  are  clearly  not  permissible.  On  a 
railway,  however,  which  is  private,  and  where  no  one 
goes  on  the  line  except  officials,  the  conditions  are 
quite  different ;  there,  a  high-voltage  current,  provided 
it  were  carried  upon  a  carefully  insulated  conductor, 
well  up  overhead  out  of  reach,  might  safely  be  per- 
mitted. 

That  only  removes  half  the  difficulty,  however,  for 
the  motors  generally  used  with  alternating  current — 
"  induction  motors,"  as  they  are  called — are  not,  gener- 
ally speaking,  suitable  for  traction  purposes.  They  do 
not  start  well,  and  it  is  not  possible  to  regulate  their 

232 


Electric  Traction 

speed  so  nicely  as  can  be  done  with  a  direct-current 
motor.  It  has  been  found,  however,  that  so  long  as 
the  current  does  not  alternate  too  rapidly,  it  can  be 
used  to  drive  a  machine  in  all  essential  respects  similar 
to  a  direct-current  motor.  The  alternating  current 
generally  used  for  electric  lighting  or  for  working 
induction  motors  alternates  as  many  as  a  hundred 
or  two  hundred  times  per  second,  but  for  this  purpose 
it  must  not  exceed  about  twenty-five  or  thirty  times  per 
second.  The  rapidity  of  alternation  is  called  the  "perio- 
dicity "  of  the  current,  and  the  motors  just  described  are 
generally  spoken  of  as  lt  single-phase  "  railway  motors, 
since  they  require  "  single-phase "  current  to  work 
them. 

Most  of  the  recent  electric  railways  are  therefore  on 
the  «  single-phase  "  system,  with  these  "  single-phase  " 
motors. 

The  current  is  carried  by  an  overhead  wire  sus- 
pended from  light  girders  which  cross  the  line  at 
frequent  intervals.  It  is  not,  however,  attached  directly 
to  the  girders,  but  is  suspended  by  means  of  wires  from 
two  other  wires  which  are  attached  to  the  girders. 
There  are  two  advantages  in  this.  First,  a  wire 
stretched  between  two  points,  no  matter  how  light  it 
may  be,  always  "  sags "  somewhat,  and  if  the  "  con- 
ductor wire  "  were  like  that  the  collector  on  the  train 
would  not  slide  smoothly  along  it  at  the  high  speed 
which  railway  trains  attain.  The  two  upper  wires,  of 
course,  sag  in  the  middle,  but  the  conductor  wire  is 
suspended  from  them  at  frequent  intervals  by  short 
wires  of  varying  lengths,  so  that  the  conductor  wire 
always  hangs  practically  straight  and  level.  The  second 
advantage  is  that  the  two  wires  can  be  insulated  from 
the  girder,  and  the  short  wires,  too,  can  be  insulated 
from  them  and  from  the  conductor  wire,  so  that  for 
current  to  escape  from  the  conductor  wire  it  would 

233 


Electric  Traction 

have  to  jump  over  two  or  even  three  separate  in- 
sulators, a  very  important  advantage  in  view  of  its 
high  voltage. 

Instead  of  a  trolley  arm  a  "  bow  collector "  is 
generally 'used.  This  consists  of  a  light  iron  frame- 
work, the  top  of  which  is  slightly  "  bowed,"  and  which 
rubs  against  the  wire  as  the  train  passes  along.  It  can 
be  lowered  flat  on  the  roof  of  the  car  when  not  in 
use.  The  raising  and  lowering  is  generally  done  by 
compressed  air. 

After  passing  from  the  conductor  wire  to  the  car 
through  the  collector,  the  current  goes  to  a  transformer 
on  the  car  itself,  which  transforms  it  down  to  a  safe 
voltage  for  use  in  the  motors.  It  then  passes  to  the 
motors  and  from  them  to  the  rails,  through  which  it 
returns  to  the  power  station. 

The  speed  is  regulated  by  means  of  a  controller, 
much  the  same  as  on  a  tramcar. 

The  brakes  on  an  electric  train  are  usually  worked 
by  compressed  air,  derived  from  a  pump  operated  by 
a  small  independent  motor. 


234 


CHAPTER   XVIII 

THE   IRON    HORSE 

THE  first  form  of  mechanical  power  that  was  used  for 
hauling  vehicles  along  a  way  formed  of  rails  was  a 
steam-engine,  and  to-day  the  steam  locomotive  remains 
the  principal  agent  for  that  purpose.  It  is  true  that 
electric  traction  has  come  into  use  on  some  lines  and 
has  proved  a  great  success,  but  it  is  quite  wrong  to 
assume,  as  some  people  do,  that  the  steam  locomotive 
will  soon  be  a  thing  of  the  past. 

On  the  contrary,  it  is  still  being  developed  ;  some  of 
the  finest  brains  are  still  occupied  in  improving  it,  and 
many  large  works  are  exclusively  employed  in  its 
manufacture.  The  truth  of  the  matter  is  that  steam 
traction  and  electric  traction  both  have  their  place  in 
the  railways  of  to-day.  The  steam  locomotive,  owing  to 
the  limitations  imposed  by  its  size  and  movability,  is 
less  efficient  than  the  stationary  engine  in  an  electric 
generating  station  ;  in  other  words,  it  needs  to  con- 
sume more  coal  in  order  to  generate  the  same  power. 
Therefore  it  pays,  under  certain  conditions,  to  generate 
the  power  in  a  stationary  engine  instead  of  on  a 
locomotive,  and  convey  it  to  the  train  by  electricity. 
The  question  is,  then,  whether  in  any  particular  case 
the  saving  in  coal  will  be  sufficient  to  compensate  for  the 
cost  of  the  electrical  apparatus  and  for  the  percentage 
of  power  which  is  lost  in  transmission  from  one  place 
to  the  other.  It  is  easy  to  see  that  on  a  short,  busy 
line  the  saving  will  be  at  the  maximum  and  the  cost 

235 


The  Iron  Horse 

of  electrification  at  the  minimum,  while  on  a  long  line 
with  few  trains  there  would  be  little  saving  in  using 
electricity,  and  the  maximum  of  expense.  Thus,  speak- 
ing generally,  we  may  say  that  for  short,  busy  lines 
electric  traction  is  best,  but  for  long  lines  steam 
traction. 

In  all  essential  particulars  every  steam  locomotive  is 
just  the  same  as  an  ordinary  stationary  engine,  but  in 
details  there  is  an  immense  variety  of  types.  The 
variations  are  due  to  many  causes,  such  as  the  character 
of  the  traffic  to  be  worked,  the  nature  of  the  line — 
whether  flat  or  hilly — and  the  particular  fancies  of  its 
designers.  It  will  be  interesting  to  notice  the  main 
points  of  difference  and  the  reasons  for  them. 

The  first  great  distinction  is  into  the  two  classes, 
goods  engines  and  passenger  engines. 

The  former  are  built  for  tractive  power  rather  than 
for  speed,  and  the  driving  wheels — those  which  are 
turned  by  the  power  of  the  steam  and  so  propel  the 
train  along — are  comparatively  small  in  diameter,  so 
that  the  power  developed  by  the  mechanism  of  the 
engine  may  not  be  partially  wasted  through  having  to 
work  through  large  wheels.  It  is  really  like  the  differ- 
ence between  the  high-gear  and  the  low-gear  on  a 
bicycle.  Many  cyclists  use  a  three-speed  gear,  and  for 
ascending  a  hill  or  for  riding  against  a  strong  wind 
they  use  the  lowest  gear,  because  though  it  takes  them 
along  more  slowly,  they  can  climb  hills  with  it  which 
would  be  impossible  on  a  high-gear.  So  the  small 
wheels  of  a  goods  engine,  though  they  prevent  it  from 
attaining  great  speed,  enable  it  to  pull  very  heavy 
loads — loads  which  would  be  beyond  the  power  of  the 
large-wheeled  passenger  engine. 

For  the  same  reason  goods  engines  have  as  many  as 
three,  four,  or  even  five  pairs  of  wheels,  all  the  same 
size,  and  coupled  together  with  cranks  and  connecting 

236 


The  Iron  Horse 

rods,  so  that  the  steam  turns  not  merely  one  pair,  but 
several.  This  gives  the  engine  a  sufficiently  good  grip 
of  the  rails  to  haul  heavy  trains.  Engines  with  three, 
four,  and  five  pairs  of  wheels  coupled  together  are  called 
"  six-coupled,"  "  eight-coupled,"  and  "  ten-coupled  " 
respectively. 

On  the  other  hand,  the  passenger  engine  has  large 
driving  wheels  and  fewer  of  them,  for  its  loads  are  not 
so  heavy  and  it  must  attain  high  speeds.  It  used  to  be 
fashionable  for  fast  passenger  engines  to  have  but  a 
single  pair  of  driving  wheels  of  very  large  diameter,  as 
much  as  eight  feet.  Such  engines  were  called  "  single 
wheel  "  engines,  a  type  which  has  gone  out  of  use 
lately  in  favour  of  "  four-coupled  "  engines,  those  in 
which  two  pairs  of  rather  smaller  wheels  are  coupled 
together. 

We  can  therefore  distinguish  the  purpose  for  which 
an  engine  is  intended  by  the  size  and  number  of  its 
driving  wheels.  Indeed,  a  little  observation  will  show 
that  the  number  of  wheels  determines  in  a  general  way 
the  whole  design  of  the  engine.  This  may  seem 
strange,  but  the  number  of  wheels  is  really  such  an 
important  feature  that  all  the  other  details  are  more  or 
less  dependent  upon  it. 

In  addition  to  the  large  wheels,  there  are  on  most 
engines  smaller  wheels,  either  in  front  or  behind,  or 
both.  These  are  not  directly  attached  to  the  engine 
itself,  but  to  a  small  truck  under  the  engine.  This 
little  truck  is  so  fixed  to  the  engine  that  it  has  a  certain 
amount  of  "  play"  :  while  still  supporting  the  engine  it 
can  move  slightly  in  relation  to  it.  This  gives  the 
engine  an  amount  of  flexibility  which  enables  it  to  pass 
easily  and  safely  round  curves  which  would  be  impos- 
sible if  all  the  wheels  were  rigidly  held  in  a  straight 
line.  But  for  this  arrangement  either  all  engines 
would  have  to  be  of  a  limited  length  or  else  the  curves 

237 


The  Iron  Horse 

would  have  to  be  made  much  less  sharp  than  they  are 
at  present.  A  truck  with  four  wheels  is  generally 
called  a  "  bogey  "  ;  one  with  two  wheels  a  "  two-wheel 
truck."  If  the  truck  is  in  front  of  the  driving  wheels  it 
is  described  as  "  front "  or  "  leading/'  and  if  behind 
them  as  "  trailing." 

An  instance  of  how  the  arrangement  of  the  wheels 
shows  the  type  is  the  very  popular  form  of  express 
passenger  engines  at  the  present  time,  known  by  the 
name  of  "  Atlantic,"  which  may  be  distinguished  in 
this  way.  They  have  a  four-wheel  leading  bogey,  then 
four  driving  wheels  (two  pairs)  coupled  together,  and 
then  a  two-wheel  trailing  truck.1 

Engines  are  again  divided  into  two  other  classes 
(the  dividing  line  cutting  right  across  the  division 
already  referred  to),  namely,  tender  engines  and  tank 
engines.  The  purpose  of  the  tender  is  to  carry  a 
supply  of  coal  and  water  for  the  journey,  and  if  an 
engine  only  goes  short  trips,  with  frequent  opportunities 
for  replenishing  its  stock,  the  tender  can  be  dispensed 
with  altogether,  for  enough  can  be  taken  on  the  engine 
itself.  In  that  case  tanks  are  fitted  to  the  engine  for 
holding  the  water,  and  so  such  come  to  be  known  as 
tank  engines. 

The  mechanism  by  which  the  steam  drives  the  wheels 

1  A  FEW  OF  THE  PRINCIPAL  TYPES  OF  LOCOMOTIVES 

American. — Four-wheel  front  truck  and  four  coupled  driving  wheels. 

Atlantic. — Four-wheel   front   truck  and  four  coupled  driving   wheels,  two- 
wheel  trailing  truck.     (For  fast  passenger  service.) 

Decapod. — Two -wheel   front   truck  and   ten  coupled  driving  wheels.     (For 
heavy  goods  service.) 

Mogul. — Two-wheel  front  truck  and  six  coupled  driving  wheels,  of  which 
middle  pair  are  connected  to  cross-head.     (For  fast  goods  trains.) 

Consolidated. — Two-wheel  front  truck  and  eight  coupled  driving  wheels  but 
no  trailing  truck.     (For  heavy  goods  service.) 

Pacific. — Four-wheel  front  truck  and  six  coupled  driving  wheels,  two-wheel 
trailing  truck.    (For  heavy  fast  passenger  service.) 
238 


The  Iron  Horse 

is  exactly  the  same  in  principle  in  a  locomotive  as  it 
is  in  a  stationary  engine.  There  are  generally  two 
cylinders,  each  with  its  piston  and  piston-rod,  cross- 
head,  connecting-rod,  and  crank,  just  as  described  in 
Chapter  II.  The  two  cranks  are  placed  at  right  angles 
to  each  other,  so  that  while  one  piston  is  at  the  end  of 
its  stroke,  just  reversing  its  direction  and  therefore 
doing  no  work,  the  other  piston  is  at  the  middle  of  the 
stroke,  and  therefore  pushing  its  hardest.  If  the^ranks 
were  put  opposite  to  each  other,  as  would  seem  to  be 
the  natural  arrangement,  there  would  be  a  "  dead 
point/'  as  it  is  called.  This  term  means  the  point  at 
which  the  connecting-rod  and  crank  form  an  exactly 
straight  line,  so  that  the  push  of  the  piston  has  no 
tendency  to  turn  the  crank  either  way.  If  a  single- 
cylinder  engine,  or  a  two-cylinder  one  with  cranks  set 
opposite,  should  by  chance  stop  on  the  "  dead  point  " 
it  cannot  start  itself,  but  needs  to  be  moved  by  some 
other  force  until  the  dead  point  is  passed.  In  large 
stationary  engines,  which  stop  at  comparatively  long 
intervals,  this  is  of  no  moment,  and  the  difficulty  is  met 
by  having  notches  cast  in  the  fly-wheel,  wherein  the 
point  of  a  crowbar  can  be  inserted  and  the  engine 
turned  a  little  way  by  hand,  or  in  some  cases  a  very 
small  engine  called  a  "  barring  "  engine  is  provided  to 
start  the  large  one. 

Either  of  these  expedients  would  be  very  incon- 
venient on  a  locomotive,  however,  so  the  cranks  are 
always  set  at  right  angles  to  each  other. 

The  cranks  are  placed  on  the  axle  of  one  of  the 
pairs  of  large  wheels,  the  other  pairs  being  coupled 
to  this  pair  by  additional  cranks  and  connecting-rods. 
These  latter  are  always  at  the  side  of  the  engine  (never 
between  the  wheels),  and  so  have  come  to  be  known  as 
"  side-rods." 

In  some  cases  the  cylinders  are  placed  outside  the 

239 


The  Iron  Horse 

wheels  of  the  engine,  and  in  others  inside,  between  the  two 
rows  of  wheels.  Engines  are  therefore  often  referred  to 
as  "outside-cylinder"  and  "inside-cylinder"  respectively. 

By  far  the  greater  number  of  locomotives  are 
"  simple/'  the  steam  from  the  boiler  going  direct  to 
both  cylinders,  but  there  are  examples  of  " compound" 
locomotives,  in  which  the  steam  goes  through  two 
cylinders  in  succession.  The  London  and  North- 
Western  Railway  (England)  used  to  build  "  three- 
cylinder  compounds."  There  were  two  small  "  out- 
side "  cylinders,  one  on  each  side,  which  formed  the 
"  high-pressure  "  cylinders,  and  the  steam  passed  from 
them  to  one  large  "  low-pressure  "  cylinder  placed  in  the 
centre,  between  the  other  two.  In  other  cases  the 
cylinder  on  one  side  is  the  "  high-pressure  "  and  that 
on  the  other  side  the  "low-pressure." 

One  English  railway  has  some  engines  with  four 
cylinders,  two  "  inside "  and  two  "  outside,"  but  they 
are  not  compound.  They  are,  in  fact,  merely  two 
ordinary  two-cylinder  "  simple  "  engines  rolled  into  one, 
and  were  designed  to  work  a  very  heavy  service  of 
passenger  trains  which  generally  needed  two  ordinary 
engines.  Very  large  and  heavy  locomotives,  however, 
while  they  are  excellent  from  the  point  of  view  of 
the  mechanical  engineer  or  locomotive  superintendent, 
since  they  reduce  the  cost  of  hauling  the  trains,  rouse 
strong  objections  from  his  colleague  the  civil  engineer, 
for  they  severely  try  the  "road"  and  increase  the  cost 
of  maintaining  it.  That  is  what  limits  the  size  of  the 
steam  locomotive. 

The  valves  which  let  the  steam  into  and  out  of  the 
cylinders  are  in  many  cases  worked  by  eccentrics,  as 
described  in  Chapter  II.,  but  there  are  also  a  number  of 
special  {t  valve  gears  "  used,  in  which,  by  an  arrange- 
ment of  levers,  the  motion  of  the  cranks  themselves  is 
made  to  work  the  valves. 

240 


The  Iron  Horse 

The  boiler  of  a  locomotive  is  of  what  is  called  the 
"  tubular  "  or  "  fire-tube"  type.  It  consists  of  a  cylin- 
drical shell  of  steel  plates  which  holds  the  water,  with 
about  200  or  more  tubes,  about  2  inches  diameter,  of 
iron,  copper,  or  brass,  running  from  end  to  end.  At 
the  back  there  is  a  large  chamber  called  the  "fire-box," 
with  iron  "fire-bars"  at  the  bottom,  forming  a  grate 
upon  which  the  fire  is  made.  The  heat  from  the  fire 
passes  through  the  tubes  into  another  chamber  at  the 
other  end,  called  the  "  smoke-box,"  at  the  top  of  which 
is  the  chimney. 

In  the  smoke-box  there  is  an  arrangement  of  the 
utmost  importance,  called  the  "  blast-pipe,"  the  in- 
vention of  which,  indeed,  by  George  Stephenson,  made 
it  possible  to  raise,  in  this  comparatively  small  boiler, 
enough  steam  for  the  engine  ;  for  it  should  be  under- 
stood that  a  locomotive  boiler  is  much  smaller,  in  pro- 
portion to  the  quantity  of  steam  which  it  is  called  upon 
to  supply,  than  a  stationary  boiler.  That  is  why, 
instead  of  one  or  two  large  flues,  there  are  a  large 
number  of  small  tubes,  so  as  to  provide  the  utmost 
possible  area  through  which  the  heat  can  pass  into 
the  water.  But  this  carries  with  it  the  disadvantage 
that  the  hot  gases  will  not  travel  so  readily  through 
the  small  tubes  ;  and,  moreover,  the  locomotive  boiler 
has  not  the  advantage  of  a  tall  chimney  to  create  a 
draught,  as  the  stationary  boiler  has.  Therefore,  unless 
some  artificial  draught  can  be  provided,  the  fire  will 
not  burn  vigorously  enough. 

This  was  one  of  Stephenson's  great  difficulties  in  the 
early  days,  until  he  hit  upon  the  happy  idea  of  the 
"  blast-pipe."  It  is  a  nozzle  placed  at  the  bottom  of 
the  smoke-box,  pointing  upwards  to  the  chimney ; 
through  it  comes  the  steam  from  the  cylinders,  shoot- 
ing upwards  in  a  powerful  jet  and  inducing  a  strong 
draught  through  the  tubes.  This  blast  is,  of  course, 

241  Q 


The  Iron  Horse 

only  in  operation  while  the  engine  is  running ;  but  for 
use  in  getting  up  steam,  or  while  standing  at  a  station, 
there  is  an  arrangement  whereby  a  jet  of  steam  straight 
from  the  boiler  can  be  directed  up  the  chimney,  so  as 
to  perform  the  same  function  that  the  blast  does  when 
the  engine  is  moving.  This  steam-jet  can  be  turned 
on  and  off  at  will  by  the  driver. 

The  "  steam  dome,"  which  forms  such  a  prominent 
feature  in  most  engines,  is  for  drying  the  steam.  When 
the  latter  arises  from  the  surface  of  the  water,  a  good 
deal  of  liquid  water  (as  distinct  from  the  vapour-steam) 
is  carried  with  it,  and  if  it  went  direct  to  the  cylinders 
this  water  would  go  too,  partially  filling  them.  The 
steam  is  therefore  taken  from  the  boiler  through  a  pipe 
whose  open  end  is  near  the  top  of  the  dome,  and  the 
steam,  by  the  time  it  has  risen  from  the  surface  of  the 
water  to  the  mouth  of  this  pipe,  has  dropped  most  of 
the  water  it  contained  and  so  reaches  the  cylinders  in 
a  dry  state.  In  some  engines,  which  have  no  dome, 
the  same  result  is  achieved  by  having  a  long  horizontal 
pipe  inside  the  boiler,  close  to  the  top.  The  steam  has 
to  enter  this  pipe  through  holes  in  the  top  of  it,  an 
arrangement  which  serves  the  same  purpose  as  the 
dome. 

The  pipe  containing  the  steam  is  then  taken  through 
the  smoke-box,  where  the  heat  is  very  great,  by  which 
means  it  is  still  further  dried. 

The  consequence  of  getting  any  considerable  quantity 
of  water  in  a  steam-engine  cylinder  is  very  serious. 
Water  is  as  incompressible  as  a  lump  of  iron,  and,  if 
there  were  more  of  it  than  would  fill  the  space  which 
is  normally  left  between  the  extreme  position  of  the 
piston  and  the  cover  at  the  end  of  the  cylinder,  the 
piston  would  be  stopped  in  its  movement  exactly  as  if 
the  cylinder  had  been  made  too  short.  The  whole  of 
the  mechanism  of  the  engine  would  be  brought  to  a 

242 


The  Iron  Horse 

sudden  stop,  unless  something  broke.  In  all  pro- 
bability the  cylinder-cover  would  be  "  blown  "  off  as  if 
by  an  explosion.  When  an  engine  starts,  the  cylinders 
are  cold  and  the  steam  condenses  copiously,  so  a  small 
cock  is  provided  at  each  end  to  let  it  out.  These  are 
called  "  drain-cocks,"  and  can  be  opened  and  closed  by 
a  system  of  rods  operated  by  the  driver.  He  always 
opens  them  when  starting,  allowing  water  (and  steam, 
too)  to  escape,  with  the  violent  hissing  noise  so  familiar 
to  us  all.  Then,  when  the  cylinders  have  become  hot 
and  the  steam  ceases  to  condense,  he  closes  them. 

So  far  we  have  considered  the  means  by  which  the 
engine  is  propelled  along,  but  it  is  almost  equally 
important  that  it  should  be  able  to  stop.  On  passenger 
trains  there  are  generally  three  independent  brakes — a 
steam-brake  on  the  engine,  a  hand-brake  on  the  tender, 
and  a  "  continuous "  brake  of  some  kind  on  every 
vehicle  in  the  train. 

The  "  hand  "  brake  is  like  that  on  a  horse-carriage, 
except  that  it  is  applied  by  a  screw  instead  of  a  lever  ; 
in  the  steam-brake  the  blocks  are  pressed  against  the 
wheels  by  steam  pushing  a  piston  in  a  cylinder  ;  while 
the  "  continuous  "  brakes  are  worked  by  air.  Of  these 
last  there  are  two  systems  in  use — the  "  vacuum  "  and 
the  "  Westinghouse." 

In  the  "  vacuum  "  there  is  a  cylinder,  placed  in  a 
vertical  position  under  each  vehicle,  with  a  piston  inside 
it  and  a  piston-rod  coming  out  through  the  bottom  end. 
Connected  with  this  there  is  an  iron  pipe,  with  a  short 
flexible  pipe  at  each  end.  When  a  man  couples  two 
vehicles  together,  he  also  couples  the  flexible  pipes,  so 
that  there  is  a  complete  pipe  running  continuously  from 
one  end  of  the  train  to  the  other.  This  is  known  as 
the  "train-pipe." 

On  the  engine  is  a  little  appliance  called  an  "  ejector." 
In  this  a  jet  of  steam  blows  through  a  nozzle  in  such  a 

243 


The  Iron  Horse 

way  that  it  sucks  the  air  from  the  train-pipe,  thus 
creating  a  vacuum  in  all  the  brake-cylinders  throughout 
the  train.  Moreover,  by  keeping  the  ejector  partially 
at  work,  the  vacuum  is  maintained  in  spite  of  the 
inevitable  small  leakage  of  air. 

In  the  brake-cylinder  there  is  a  small  tl  non-return  " 
valve,  which  permits  the  air  to  be  sucked  from  both 
sides  of  the  piston  equally  ;  there  is  nothing  then  to 
keep  the  piston  up,  so  it  falls  to  the  bottom  of  the 
cylinder  by  its  own  weight,  and  the  brake  is  then  off. 
As  soon  as  the  train  needs  to  stop,  however,  the  driver, 
by  the  movement  of  a  handle,  stops  the  ejector  and 
admits  air  to  the  "  train-pipe."  This  enters  the  lower 
part  of  the  cylinder,  but  is  prevented  by  the  "  non- 
return "  valve  from  entering  the  upper  part.  There  is 
therefore  the  full  pressure  of  the  atmosphere  under  the 
piston,  and  a  vacuum  above  it,  so  that  the  piston  is 
pushed  upward,  a  movement  which  is  communicated 
by  the  piston-rod  to  a  system  of  cranks  and  levers  which 
press  the  blocks  against  the  wheels. 

The  guard  also  can,  in  an  emergency,  admit  air  to 
the  train-pipe  and  so  put  on  the  brake,  and  in  the  event 
of  a  coupling  breaking,  so  that  the  train  comes  in  two, 
the  flexible  connection  becomes  broken,  air  rushes  in, 
and  the  brake  is  applied  to  both  parts  of  the  train  auto- 
matically. Hence  this  system  is  styled  the  "  automatic 
vacuum  brake,"  and  vehicles  fitted  with  it  can  often  be 
distinguished  by  the  initials  "  A.  V.  B."  marked  on  them. 

Of  course,  the  same  inrush  of  air  takes  place  when  a 
vehicle  is  uncoupled  from  its  train,  so  that  just  at  the 
moment  when,  probably,  it  has  to  be  pushed  by  hand 
or  pulled  by  a  horse,  it  becomes  immovable.  This  is 
provided  for  by  a  loop  of  wire  placed  in  a  convenient 
position  on  either  side  of  the  vehicle.  It  is  only  necessary 
for  a  man  to  pull  one  of  these,  when  it  opens  a  valve 
and  lets  air  in  to  both  sides  of  the  piston,  the  result 

244 


The  Iron  Horse 

being  just  the  same  as  it  is  when  there  is  a  vacuum  both 
sides  ;  the  piston  descends  by  its  own  weight,  and 
releases  the  brake.  As  soon  as  it  is  coupled  to  an 
engine  again,  the  ejector  withdraws  the  air  from  both 
sides  of  the  piston,  and  it  is  then  ready  to  go  "  on  " 
again  as  soon  as  it  is  needed. 

With  this  brake  a  train  of  twelve  carriages,  going  at 
60  miles  an  hour,  can  be  stopped  in  400  yards  in  25 
seconds. 

The  "  Westinghouse  Automatic  "  brake,  which  works 
by  compressed  air,  is  a  little  more  complicated  than  the 
"  vacuum."  Again  there  is  a  cylinder  and  piston  under 
each  vehicle,  the  movement  of  the  piston  being  arranged 
to  apply  the  brake-blocks  to  the  wheels.  In  addition 
to  that,  however,  there  is  a  reservoir  for  compressed 
air,  and  a  very  ingenious  contrivance  known  as  the 
"  triple-valve."  Pipes  with  flexible  connections  form 
a  complete  "  train-pipe,"  running  the  whole  length  of 
the  train. 

On  the  engine  there  is  a  little  steam-pump  which 
compresses  air  into  a  large  reservoir  underneath  the 
engine,  to  a  pressure  of  about  ninety  pounds  per  square 
inch,  and,  when  the  driver  moves  a  handle,  this  com- 
pressed air  passes  through  the  train-pipe  to  the  triple- 
valves. 

Let  us  suppose  that  the  brake  has  just  been  applied. 
The  cylinders  are  all  full  of  compressed  air,  which 
is  forcing  the  pistons  forward  and  holding  the  blocks 
tightly  against  the  wheels.  When  the  driver  wishes  to 
release  the  brakes,  he  moves  the  handle  and  permits 
compressed  air  to  pass  along  the  train-pipe  to  the 
triple-valves.  These  are  so  arranged  that  under  these 
circumstances  they  supply  air  to  the  reservoirs,  but 
let  the  air  out  from  the  cylinders,  so  that  the  pistons 
are  free  to  move  backwards  and  release  the  brakes. 
Thus  the  one  action  of  sending  a  supply  of  air  along 

245 


The  Iron  Horse 

the  train-pipe  releases  the  brakes  and  replenishes  the 
store  of  air  ready  for  the  next  application. 

This  state  of  things  continues  until  the  train  needs 
to  stop  again.  Another  movement  of  the  same 
handle  then  shuts  off  the  supply  of  air  to  the  train- 
pipe,  and  lets  out  the  air  which  the  pipe  already 
contains.  At  first  sight  it  seems  strange  that  a  com- 
pressed-air brake  can  be  applied  by  liberating  the 
compressed  air,  but  the  explanation  lies  in  the  triple- 
valve.  As  soon  as  the  supply  is  shut  off,  and  the 
pressure  in  the  train-pipe  allowed  to  fall  below  that 
in  the  reservoirs,  this  remarkable  little  valve  disconnects 
the  reservoirs  from  the  train-pipe,  but  connects  the 
reservoirs  to  the  cylinders.  Thus  the  pistons  are 
pushed  forward  and  the  brake  applied. 

The  guard,  too,  has  a  handle  by  which  he  can 
let  out  the  air  from  the  train-pipe,  and  so  stop  the 
train  even  in  spite  of  the  driver.  The  same  thing 
happens  automatically  if  the  train  should  be  severed. 

The  whole  secret  of  the  thing  resides  in  the  triple- 
valve — a  beautiful  piece  of  mechanism,  but  unfortunately 
too  complicated  for  a  detailed  explanation  here. 

Readers  may  be  tempted  to  inquire  which  is  the 
better  of  these  two  systems,  but  that  is  a  question 
to  which  no  answer  can  be  given.  Some  railways 
prefer  one  and  some  the  other. 

Goods  trains,  with  few  exceptions,  have  no  con- 
tinuous brakes.  The  slow  speed  at  which  they  travel 
renders  them  unnecessary.  They  depend  upon  the 
brake  on  the  engine  and  tender,  and  also  the  hand- 
brakes applied  by  the  guards  in  the  two  vans. 

When  speaking,  earlier  in  this  chapter,  of  the 
purpose  of  a  "  tender,"  reference  was  made  to  the 
supply  of  water.  On  a  long  " non-stop"  run  the 
largest  tender  is  unable  to  carry  sufficient,  so  some 
device  is  necessary  by  which  water  can  be  taken 

246 


The  Iron  Horse 

"on  board"  without  stopping  the  train.  This  is 
done  by  means  of  a  trough  and  scoop.  Some  spot 
is  chosen  where  there  is  a  stretch  of  perfectly  level 
line,  and  there  a  narrow  trough  is  placed  between  the 
rails,  perhaps  nearly  a  mile  long.  Under  the  tender 
there  is  a  hinged  scoop  which  can  be  let  down  when 
required.  On  reaching  the  trough  the  driver  lets 
down  this  scoop,  with  its  mouth  in  the  direction  in 
which  the  train  is  moving.  The  motion  of  the  train, 
without  pumping  or  other  aid,  then  causes  the  water 
to  rush  up  from  the  trough  into  the  tender,  until  the 
latter  is  full.  Then  the  scoop  is  drawn  up  again. 

The  very  latest  form  of  locomotive  is  worked  by  a 
steam-turbine.  This  is  an  experiment  which  is  being 
made  by  a  great  British  firm  of  locomotive  builders. 

The  whole  structure  is  supported  on  two  four-wheel 
bogies,  one  pair  of  wheels,  in  each,  forming  the  driving- 
wheels.  The  boiler  is  of  the  usual  locomotive  type, 
and  the  coal  and  water  are  carried  in  tanks  and  bunkers 
on  either  side  of  it.  From  the  boiler  the  steam  goes 
to  the  turbine,  which  works  at  the  enormous  speed  of 
3000  revolutions  per  minute,  and  drives  a  dynamo  which 
supplies  current  to  four  motors.  Two  of  these  have 
their  armatures  mounted  on  each  of  the  axles  of  the 
driving-wheels.  The  turbine  thus  works  at  a  constant 
high  speed,  the  conditions  which  suit  it  best,  and  the 
speed  of  the  driving-wheels  is  regulated  electrically. 

A  novel  feature  in  a  locomotive  is  that  the  steam  is 
condensed,  thereby  adding  to  the  power  of  the  turbine, 
and  also  saving  the  water,  which  is  pumped  back  into  the 
boiler.  The  water  carried  in  the  tanks  is,  therefore,  only 
used  for  condensing  the  steam.  A  small  pump  delivers 
it  from  the  tanks  to  the  condenser.  Then  a  second 
pump  sends  it  along  to  a  "  cooler,"  which  is  placed  in 
the  front  of  the  engine  in  order  to  get  the  full  benefit 
of  the  blast  of  cold  air  caused  by  the  motion  of  the 

247 


The  Iron  Horse 

train,  and  from  the  cooler  it  goes  back  to  the  tanks. 
Since  the  steam  is  condensed  there  can,  of  course,  be 
no  steam-blast  to  urge  the  fire,  so  a  small  fan  is  em- 
ployed which  forces  air  from  the  neighbourhood  of  the 
cooler  (where  it  has  become  somewhat  heated)  into 
the  fire-box.  Thus  something  of  a  regenerative  system 
is  established,  waste  heat  from  the  condensed  steam 
being  carried  back  to  the  fire. 

Although  intended  for  main-line  express-passenger 
work,  this  engine,  it  will  be  noticed,  is  without  the  large 
driving-wheels  usual  in  engines  for  that  kind  of  service, 
and  it  may  be  interesting  to  notice  the  reason  for  this 
difference.  In  an  ordinary  "  reciprocating "  engine 
two  strokes  of  the  piston  make  one  revolution  of  the 
crank ;  therefore,  in  a  locomotive,  two  strokes  of  the 
piston  represent  a  distance  travelled  equal  to  the  cir- 
cumference of  the  driving-wheels.  An  increase  in 
speed  may  therefore  be  secured  in  two  ways — one  by 
increasing  the  number  of  strokes  per  minute,  and  the 
other  by  increasing  the  size  of  the  wheels.  Now  there 
is  a  practical  limit  to  the  speed  of  the  piston.  If  it  be 
too  great  it  subjects  the  whole  mechanism  to  excessive 
wear  and  tear,  and  there  is  also  a  difficulty  in  getting 
the  exhaust-steam  out  of  the  cylinder  quickly  enough. 
Therefore  engines  for  fast  traffic  are  made  with  large 
wheels,  so  as  to  keep  the  speed  of  the  piston  within 
proper  limits.  This  difficulty,  however,  does  not  apply 
to  electric  motors,  which  work  well  at  high  speeds, 
so  that  in  the  case  of  the  turbine-locomotive  the 
driving-wheels  may  be  made  comparatively  small,  their 
small  circumference  being  compensated  by  the  rapidity 
with  which  they  turn  round. 


248 


CHAPTER  XIX 

HOW   RAILWAYS   ARE   WORKED 

IN  this  chapter,  and  the  next  one  also,  I  arn  compelled 
to  draw  my  descriptions  mainly,  though  not  entirely, 
from  what  is  done  in  Great  Britain.  The  reason  for 
this  is  that,  owing  to  the  special  conditions  which  obtain 
in  that  country,  the  management  and  signalling  arrange- 
ments have  to  be  of  the  most  elaborate  character.  For 
one  thing  it  is  a  small  country,  so  that  it  has  no  great 
trunk  lines — as  the  term  is  understood  in  the  United 
States,  for  instance — but,  on  the  other  hand,  it  has  certain 
very  densely  populated  districts.  Thus  the  lines  are 
short,  but  crowded  with  trains,  necessitating  an  elabo- 
rate care  to  prevent  accidents  which  is  absolutely  un- 
necessary elsewhere. 

There  was  a  good  story  going  about  a  little  while 
ago.  Two  men  were  talking  in  the  train,  and  one  of 
them  made  the  assertion  that  it  is  never  safe  to  trust  a 
man  farther  than  you  can  see  him.  The  reply  was 
brief,  but  crushing :  t{  Can  you  see  the  man  who  is 
driving  this  train  ?  " 

I  mention  this  story  because  it  brings  out  a  fact 
which  we  seldom  fully  realise.  When  we  calmly  take 
our  seats  in  a  railway  carriage,  and  without  a  thought 
of  danger  allow  ourselves  to  be  whirled  along  at  sixty 
or  seventy  miles  an  hour,  we  are  putting  unlimited  con- 
fidence in  a  large  number  of  men  who  are  individually 
quite  unknown  to  us.  Nor  is  our  confidence  misplaced, 
for  a  railway  train  is  one  of  the  safest  places  on  the 
face  of  the  earth. 

249 


How  Railways  are  Worked 

Let  us  see,  therefore,  who  these  men  are  to  whom 
we  entrust  our  lives,  and  how  they  do  their  work. 

We  naturally  think  first  of  the  engine-driver.  What 
a  task  his  is !  He  is  expected  to  know  every  inch  of 
as  much  as  400  miles  of  line.  He  must  be  familiar 
with  the  position  of  every  signal,  know  where  every 
gradient  is  (even  in  the  dark),  how  steep  it  is,  where  the 
curves  are  at  which  he  must  reduce  speed,  and  how 
fast  he  may  go  through  stations  and  junctions.  He 
must  know  all  these  things,  too,  with  such  certainty  that 
he  will  not  hesitate  to  drive  a  train  through  the  dark 
at  a  high  speed  if  necessary.  Then  when  we  think  how 
his  sight  may  be  impeded  by  rain,  or  other  atmospheric 
conditions,  his  work  appears  more  difficult  still.  It  has 
often  seemed  almost  incredible  to  me  that  any  man  can 
have  sufficient  "  nerve  "  to  drive  a  fast  express  at  night. 
Yet  we  know  that  hundreds  do  it  every  day,  and  with 
perfect  safety. 

Then,  on  the  top  of  all  this,  he  must  keep  his  eye  on 
his  watch  and  on  his  Working  Time-table.  At  the  end 
of  his  journey  he  has  to  write  out  a  journal  for  the  in- 
spection of  his  superiors,  and,  if  he  has  been  late  any- 
where, he  must  state  the  reason.  The  guard  keeps  a 
similar  journal,  and  records  are  kept  too  in  all  the  signal- 
cabins,  so  that  any  failure  to  keep  proper  time  can  be 
inquired  into,  and  if  it  is  found  to  be  due  to  the  driver's 
fault  he  gets  into  trouble. 

The  Working  Time-table  is  a  private  (book  issued  to 
the  company's  servants  only,  and,  on  an  important  line, 
it  is  a  most  wonderful  volume.  It  generally  runs  into 
hundreds  of  pages  ;  on  the  Great  Western  Railway,  the 
largest  line  in  England,  it  is  three  or  four  inches  thick. 
In  addition  to  the  information  given  in  the  public  time- 
tables, it  contains  the  times  when  trains  pass  different 
places,  not  simply  where  they  stop  ;  and  also  it  shows 
goods-trains,  empty  trains,  light  engines  (that  is  to  say, 

250 


How  Railways  are  Worked 

engines  without  a  train,  going  to  or  coming  from  their 
work),  and  a  lot  of  other  details  which  the  public  do  not 
need  to  know. 

There  is  also  an  "  appendix  "  to  the  Working  Time- 
table which  gives  us  all  the  standing  instructions  by 
which  the  working  of  the  line  is  regulated — such  as  the 
rules  for  block-working,  to  which  I  shall  refer  presently. 

Then,  in  addition  to  the  Working  Time-table,  there 
are  notices  of  special  traffic  which  are  issued  weekly. 
If,  for  instance,  the  engineer's  department. needs  to  have 
possession  of  the  line  at  some  point  one  night  or  on 
Sunday,  to  make  some  repairs,  the  fact  has  to  be 
published  in  the  weekly  notice  with  all  the  necessary 
instructions  to  all  who  may  be  concerned.  If  a  Sunday- 
school  or  a  club  have  a  special  excursion  train,  full 
particulars  have  to  go  in  the  weekly  notice. 

A  driver  has  copies  of  all  these  sent  him,  and  he  has 
to  pick  out  and  remember  anything  which  may  concern 
him. 

He  has,  too,  to  rely  largely  upon  himself.  His 
colleague,  the  signalman,  has  many  ingenious  devices  to 
keep  him  from  making  an  error,  but  not  so  the  driver. 
For  example,  it  is  possible  that  he  may  approach  a  sharp 
curve  at  too  high  a  speed,  as  a  driver  did  at  Salisbury 
some  years  ago,  causing  a  bad  accident,  and  there  is 
nothing  whatever  but  his  own  knowledge  of  the  road 
to  prevent  him  doing  so.  It  is  true  that  he  has  the 
assistance  of  the  fireman ;  but  he  has  his  fire  to  see  to, 
and,  as  on  a  hundred-mile  trip  he  will  have  to  shovel 
perhaps  as  much  as  three  tons  of  coal,  it  is  evident  that 
he  cannot  be  on  the  look-out  all  the  time.  Thus  the 
driver's  responsibility  is  very  great. 

He  begins  his  career  as  a  cleaner  in  the  engine-sheds, 
where  he  learns  all  about  the  engines.  Then  he 
becomes  a  fireman,  and  then  a  driver  of  goods  trains, 
afterwards  passing  to  slow-passenger  and  then  to 

251 


How  Railways  are  Worked 

express-passenger  trains.  Finally,  he  usually  goes  back 
a  step,  for  an  elderly  man  does  not  as  a  rule  feel  equal 
to  the  strain  of  express  driving ;  so,  after  passing  the 
prime  of  life,  he  generally  settles  down  to  the  less 
exacting  and  more  regular  work  of  driving  a  slow 
branch  or  suburban  train. 

But,  however  good  drivers  may  be,  they  cannot  save 
a  train  from  disaster  if  the  road  on  which  it  runs  is  not 
perfect,  and  this  brings  us  to  another  lot  of  men  of 
whom  we  hardly  ever  think  at  all.  I  mean  the  men 
who  look  after  the  permanent  way — that  is  to  say,  the 
actual  rails  on  which  the  train  runs,  with  the  chairs  and 
sleepers  by  which  they  are  supported.  It  is  called 
11  permanent "  because  when  a  railway  is  being  made 
the  contractors  put  down  a  temporary  way  for  their 
own  use,  and,  when  the  embankments,  cuttings,  tunnels, 
and  so  on  are  finished,  this  temporary  way  is  pulled  up 
and  replaced  by  a  "  permanent  way." 

The  line  is  divided  up  into  lengths  of,  generally, 
about  two  miles,  and  a  gang  of  men  called  platelayers 
are  appointed  to  look  after  each  length.  They  go  up 
and  down  all  day  long  tightening  up  bolts,  driving  in 
spikes,  occasionally  putting  in  a  new  sleeper,  or  in  some 
such  way  keeping  the  line  up  to  a  high  state  of 
perfection.  The  chief  man  in  the  gang  is  called  the 
ganger,  and  one  of  his  duties  is  to  walk  over  his  length 
twice  every  week-day  and  once  on  Sunday.  Thus  the 
line  is  inspected  thirteen  times  a  week,  and  the  value  of 
this  inspection  is  illustrated  by  the  following  incident. 

I  remember  once  passing  through  a  tunnel  near 
London,  at  one  end  of  which  I  noticed  a  gathering  of 
high  officials.  A  few  hours  later  I  learnt  that  the 
ganger  of  the  length  had  that  morning  noticed  some- 
thing wrong  with  the  brick  lining  of  the  tunnel.  It 
was  found  to  be  unsafe,  and  had  to  be  closed  immedi- 
ately. My  train  was  the  last  that  went  through  until 

252 


How  Railways  are  Worked 

it  had  been  reconstructed.  The  vigilance  of  that  man 
had  possibly  averted  a  terrible  disaster. 

The  name  platelayer  is  a  survival  from  the  old  times, 
when  the  rails  were  flat  plates  of  iron,  supported  at 
intervals  on  blocks  of  stone.  They  were  then  made  of 
cast  iron,  and  later  of  wrought  iron,  but  now  rails  are 
always  made  of  steel.  The  latter  is  cheaper,  and,  as  it 
is  stronger,  a  steel  rail  can  be  allowed  to  wear  down 
much  more  than  an  iron  one  before  it  is  renewed. 
The  sleepers  are  generally  of  timber,  well  creosoted  to 
keep  them  from  rotting. 

The  platelayers  also  work  the  fog-signals  in  foggy 
weather.  They  are  all  attached  for  this  purpose  to 
certain  signal-boxes,  and,  as  soon  as  a  fog  comes  on, 
each  man  repairs  to  the  cabin,  gets  his  fog-signals,  and 
goes  to  his  post.  It  is  all  carefully  arranged,  so  that,  in 
the  event  of  a  fog  coming  on  suddenly,  no  time  is  lost. 

Now  we  come  to  the  signalman.  A  signalman's 
duties  are  very  important  and  onerous,  particularly  at 
large  stations  and  junctions,  and  in  the  past  there  have 
been  many  serious  accidents  through  signalmen's 
mistakes.  Every  accident,  however,  set  ingenious 
minds  to  work  to  devise  systems  and  appliances  by  which 
such  accidents  should  be  made  impossible  in  the  future. 
A  modern  signalman  therefore  has  a  carefully  devised 
system  to  work  to,  and  many  clever  appliances  to  keep 
him  from  making  a  mistake,  but  still  a  great  deal  depends 
upon  the  man  who  has  to  work  them. 

At  first  there  were  no  signals  at  all  on  the  early 
railways  ;  but  after  a  time  a  station-master,  on  the 
Stockton  and  Darlington  line  (England),  hit  upon  the 
idea  of  putting  a  lighted  candle  in  his  .window  when  he 
wanted  a  train  to  stop,  and  out  of  that  simple  invention 
the  signalling  methods  of  to-day  have  grown  up.  By 
easy  stages  there  was  evolved  the  post,  with  an  arm  for 
signalling  by  day  and  a  lamp  for  use  at  night,  such  as 

253 


How  Railways  are  Worked 

we  are  all  familiar  with  now.  This  was  as  early  as 
1842,  but  although  the  post  and  arm  were  then  practi- 
cally the  same  as  they  are  now,  the  method  of  working 
them  was  very  different.  Each  signal  was  worked  by 
a  lever  at  the  bottom  of  the  post  and  each  set  of  points 
by  a  lever  near  them.  Several  years  later,  however, 
a  signalman  had  a  brilliant  inspiration.  He  thought  of 
working  a  signal  from  a  distance  by  pulling  a  wire. 
This  seems  ridiculously  simple  to  us ;  but  it  was  then 
a  really  important  invention,  and  it  made  possible  the 
great  system  of  "  interlocking  "  to  which,  more  than  to 
anything  else,  we  owe  our  safety  to-day. 

Under  this  plan  all  the  signals  are  worked  by  wires 
from  a  central  position,  and  the  points  are  worked  by 
rods  from  the  same  place.  This  central  position  is 
always  enclosed  for  the  protection  of  the  appliances, 
and  of  the  man  working  them,  and  thus  we  get  the 
modern  signal-cabin.  In  this  cabin  there  are  a  row  of 
levers,  one  for  each  signal  or  set  of  points,  and  these 
levers  are  made  to  interlock  with  each  other  so  that 
they  can  only  be  pulled  in  proper  combinations. 

This  system,  though  it  originated  more  than  fifty 
years  ago,  is  in  use  to-day  to  a  greater  extent  than  ever 
on  all  the  railways  in  England,  and  also  in  America. 
I  will  therefore  give  a  simple  illustration  of  it. 

Here  we  have  three  plans  of  a  small  junction,  and 
I  show  a  set  of  points  and  a  signal  forming  three 
different  combinations.  The  first  two  are  quite  safe, 
and  therefore  it  is  possible  for  the  signalman  to  make 
them.  The  third,  however,  is  dangerous,  because  it 
would  permit  a  train  to  go  from  A  towards  B,  and 
another  from  C  towards  D  at  the  same  time,  and  they 
might  collide  at  the  crossing.  The  lever  which  works 
the  points,  and  that  which  works  the  signal,  are  therefore 
interlocked  so  as  to  render  such  a  combination  impossible. 
As  soon  as  the  points  are  set  to  send  a  train  along  the 

254 


How  Railways  are  Worked 

branch,  the  signal  is  locked  at  danger.  On  the  other 
hand,  as  soon  as  the  signal  has  been  lowered,  the  points 
are  locked  in  the  straight  ahead  position. 

Writers  of  fiction,  and  still  more  poets,  would  often 
be  the  better  off  for  a  little  knowledge  of  the  working 
of  railways.  I  well  remember  having  heard  a  recitation 


No.  I 


Ho.  I  **" 


FIG.  39. — Diagrams  illustrating  the  principle  of  interlocking.  One  signal  and 
one  set  of  points  shown.  Nos.  I  and  2  are  safe  combinations,  and  can 
be  made.  No.  3  is  dangerous,  and  cannot  be  made.  Arrows  indicate 
trains. 

relating  to  a  signalman  who  went  to  sleep  on  duty.  I 
forget  the  whole  story,  but  these  words  I  remember 
very  clearly : — 

"  When  the  roar  of  the  '  limited '  woke  me, 
And  I'd  got  the  line  to  clear." 

These  words  can  only  mean  that  while  he  was  asleep 
an  express  train  had  approached  at  full  speed,  and  there 
was  something  on  the  line  which  he  had  got  to  get  out 

255 


How  Railways  are  Worked 

of  the  way  before  it  reached  him.  Now  such  a  state 
of  things  is  quite  impossible — in  England,  at  any  rate. 
The  worst  that  would  happen  if  a  signalman  went  to 
sleep  would  be  that  a  train,  if  it  came  along,  would  have 
to  wait,  no  matter  how  important  a  train  it  might  be, 
at  the  cabin  in  the  rear  until  somebody  or  something 
woke  him  up. 

This  is  ensured  by  a  system  called  the  "  block 
system."  It  is  enforced  by  Act  of  Parliament,  and  is 
embodied  in  a  code  of  regulations  of  which  every  official 
on  a  railway  has  a  copy,  and  with  which  they  all  have 
to  be  familiar. 

Its  main  principle  is  this.  The  line  is  divided  up 
into  sections  which  are  separated  from  each  other  by  a 
signal-cabin  and  a  set  of  signals,  and  only  one  train  is 
allowed  in  a  section  at  a  time.  At  each  cabin  there  are 
two  signals  for  each  line.  The  one  at  the  side  from 
which  the  train  approaches  is  called  the  home  signal, 
and  the  other,  which  is  a  little  way  on  the  further  side, 
is  called  the  starting  signal.  The  cabins  are  in  tele- 
graphic communication  with  each  other,  and  before  a 
signalman  may  allow  a  train  to  pass  the  home  signal, 
he  must  inquire  of  the  man  in  the  next  cabin  whether 
the  line  is  clear,  and  the  latter  must  not  reply  in  the 
affirmative  unless  the  previous  train  has  passed  safely 
and  everything  is  clear.  He  obviously  could  not  give 
this  reply  if  he  were  asleep,  so  that  to  bring  about  the 
conditions  mentioned  in  the  poem,  the  train  would  have 
had  to  run  past  both  the  home  and  starting  signals  at 
the  previous  cabin  while  they  stood  at  danger,  not  to 
mention  the  distant  signal,  an  indicator  which  is  placed 
1000  yards  farther  back  still  to  warn  the  driver  when 
the  home  signal  is  against  him. 

But  some  of  my  readers  may  be  tempted  to  ask, 
What  is  the  good  of  the  starting-signal,  and  why  is  it  so 
called  ?  In  the  first  place  it  is  an  additional  safeguard, 

256 


How  Railways  are  Worked 

as  just  explained,  because  while  a  driver  might  pass 
one,  it  is  inconceivable  that  he  would  pass  two  signals 
at  danger  ;  and,  in  the  second  place,  it  is  useful  in  this 
way.  Very  often  a  cabin  is  at  a  station,  the  platform 
being  between  the  two  signals,  and  it  would  be  a  useless 
waste  of  time  to  keep  a  stopping  train  standing  just 
beyond  the  end  of  the  platform  simply  because  there 
was  a  train  in  the  section  ahead,  perhaps  a  mile  away. 
Under  these  conditions  therefore  a  signalman  may, 
after  the  train  has  nearly  stopped,  lower  his  home  signal 
and  allow  it  to  draw  slowly  up  to  the  starting  signal, 
but  there  it  must  stop  until  the  section  ahead  is  clear. 

It  is,  in  fact,  an  invariable  rule  that  thmgs  shall  be  so 
devised  that  any  failure,  either  of  a  man  or  an  apparatus, 
shall  result  in  stopping  the  traffic  rather  than  incurring 
the  slightest  risk.  We  have  just  seen  how  the  sudden 
illness  or  the  falling  asleep  of  a  signalman  would  only 
stop  the  traffic,  and  in  just  the  same  way  the  signals  are 
so  constructed  that  if  anything  breaks  they  at  once  go 
to  danger,  and  all  the  electrical  appliances  which  are 
used  give  a  danger  indication  in  the  event  of  the 
current  failing. 

Probably  every  one  has  heard,  while  waiting  at  a 
station,  sounds  as  of  the  striking  of  a  small  gong  pro- 
ceeding from  the  signal-cabin.  Those  sounds  are  the 
audible  signs  given  by  the  special  electric  telegraph 
instruments  by  which  the  block  system  is  worked. 

Let  us  in  imagination  go  into  the  signal-cabin  and 
for  the  moment  assume  the  duties  of  signalman.  For 
distinction  we  will  call  our  cabin  B,  the  next  one  in  the 
direction  of  the  capital  (which  we  call  the  "  up  "  direc- 
tion) shall  be  A,  and  the  next  in  the  opposite  direction 
C.  We  will  also  assume  that  it  is  on  an  ordinary  double 
line. 

In  front  of  us  there  will  be  a  row  of  levers,  and 
above  them,  on  a  shelf,  four  instruments  something  like 

257  R 


How  Railways  are  Worked 

clocks.  These  are  the  block-telegraph  instruments, 
and,  in  the  centre  of  the  dial  on  each,  there  will  be  a 
little  pointer  like  the  needle  of  a  toy-compass.  All  the 
needles  will  be  upright,  and  will  point  to  the  words 
"  Line  blocked  "  J  printed  on  the  dials.  We  shall  notice, 
too,  that  to  one  side  of  each  dial  there  are  the  words 
"  Line  clear,"  and  opposite  to  them  "  Train  on  line." 

At  the  base  of  every  alternate  instrument  there  is  a 
handle  which  hangs  down  vertically,  and  to  every  pair 
of  telegraph  instruments  there  is  a  separate  instrument 
(known  as  a  bell  instrument,  since  a  bell  is  its  chief 
feature),  with  a  gong  on  the  top  and  a  handle  below. 
Our  gong  can  be  rung  by  the  man  in  the  next  cabin 
while  the  handle  enables  us  to  ring  a  similar  gong  in 
his  cabin. 

Suddenly  there  is  a  sound  on  the  bell  instrument 
marked  tl  A  and  B,"  four  strokes  in  rapid  succession. 
Our  colleague  at  A  is  asking  us,  "  Is  line  clear  for 
express-passenger  train  ?  "  We  then  look  at  the  block 
telegraph  instrument  marked  "A  and  B  down  line" 
(for  if  a  train  is  coming  from  A,  which  is  on  the  up  side 
of  us,  it  must  be  a  down  train),  and  there  we  see  that 
the  needle  is  pointing  to  "  Line  blocked,"  at  which 
position  it  was  placed  when  the  last  down  train  passed 
us.  This  confirms  our  recollection  that  the  previous 
train  has  safely  preceded  on  its  way,  and,  after  satisfying 
ourselves  that  all  is  clear  about  our  own  cabin,  we  turn 
the  vertical  handle  of  our  instrument  to  the  right  and 
secure  it  there  with  a  little  pin.  Immediately  our 
needle  points  to  "  Line  clear,"  and  the  corresponding 
needle  in  A  cabin  does  the  same.  From  this  the  man 
at  A  knows  that  he  may  let  the  train  come  forward,  and 
he  then  lowers  his  signals. 

Presently  there  are  two  rings  on  the  bell,  which 
means  "  Train  entering  section,"  and  we  then  unpin 

1  Here  we  see  the  origin  of  the  term  "  block  system." 

258 


How  Railways  are  Worked 

our  handle  and  turn  it  to  the  left,  making  both  our 
needle  and  A's  point  to  "Train  on  line."  Finally, 
when  the  train  passes  us,  we  give  A  three  rings,  with 
a  pause  between  the  second  and  third,  which  means 
"  Train  passing  out  of  section,"  and  then  we  unpin  our" 
handle  again,  and  let  it  hang  down  vertically.  Both 
needles  then  go  to  "  Line  blocked,"  and  there  they  stop 
as  an  indication  that,  if  nothing  happens  in  the  mean- 
time, we  may  give  "  Line  clear  "  to  A  for  another  train, 
as  soon  as  one  comes  along. 

In  the  meantime  we  have  of  course  rung  up  C  on 
the  "  B  and  C "  bell  instrument,  with  four  beats,  to 
which  he  would  reply  just  as  we  did  to  A. 

The  bell  signals,  I  ought  to  explain,  are  always 
repeated  by  way  of  answer,  and  to  make  sure  that 
they  are  properly  understood,  but  I  did  not  mention 
these  replies  in  the  foregoing  description  for  the  sake 
of  simplicity. 

The  instruments  just  described  are  not  exactly  the 
same  on  all  lines.  In  some,  for  instance,  there  is  only 
one  for  each  direction  instead  of  two,  and  it  has  two 
needles ;  but  they  are  all  on  the  same  principle,  and,  if 
a  reader  should  ever  see  one  of  a  different  type,  he 
will  have  no  difficulty  in  understanding  it  from  what  I 
have  just  said. 

The  great  bulk  of  the  traffic  in  this  country  is  worked 
under  this  system,  but  it  is  clear  that  it  does  not  render 
a  mistake  on  the  part  of  the  signalman  absolutely  im- 
possible. For  instance,  nothing  but  his  own  care  and 
attention  to  the  proper  routine  prevents  a  man  from 
giving  the  "  Line  clear  "  signal,  when  in  fact  the  train 
has  not  yet  passed,  or  from  pulling  off  his  signals  before 
he  gets  "  Line  clear  "  from  the  other  cabin,  so  some 
lines  use  a  further  development  whereby  a  mistake  is 
made  almost  an  impossibility.  This  is  called  the  "  lock 
and  block  system." 

259 


How   Railways  are  Worked 

The  instruments  are  in  this  case  somewhat  different, 
and  they  are  made  to  interlock  with  certain  signal- 
levers,  and  also  are  connected  electrically  to  an  ap- 
paratus called  a  treadle,  which  the  train  works  as  it 
passes  over  it. 

When  the  lever  of  the  starting  signal  has  been  put 
to  danger,  it  becomes  locked,  and  cannot  be  pulled 
again  until  the  man  in  the  next  cabin  sends  a  "  Line 
clear  "  message  which  automatically  unlocks  the  lever. 

The  man  in  the  other  box,  too,  when  he  has  once 
sent  a  "  Line  clear  "  message  finds  his  instrument  locked, 
so  that  he  cannot  send  the  same  message  again  until 
the  train  has  arrived  and  passed  over  the  treadle. 

Thus,  a  signalman  cannot  possibly  make  either  of 
the  mistakes  referred  to  just  now.  In  fact,  at  places 
where  there  are  no  points  where  shunting  may  have  to 
be  done,  the  signalman  becomes  merely  an  automaton. 

I  expect  readers  will  wonder  why  such  an  apparently 
perfect  system  as  this  is  not  adopted  universally.  One 
reason  is  that  the  men  are  so  well  trained,  and  work 
the  ordinary  block  system  so  methodically,  that  it  is 
in  practice  as  safe  as  the  "lock  and  block"  system. 
The  second  is  that  it  is  allowable  at  certain  places,  and 
under  certain  conditions,  to  modify  the  block  system 
slightly.  At  these  particular  cabins,  if  a  man  gets  the 
message  "  Is  line  clear  ? "  while  a  train  is  standing 
between  his  home  and  starting  signals,  he  must  not 
reply  "  Line  clear,"  but  he  may  give  a  bell  signal,  mean- 
ing "Section  clear,  but  station  blocked."  The  other 
man  must  then  stop  the  approaching  train  dead,  and  tell 
the  driver  verbally  that  he  may  proceed  cautiously  as 
far  as  the  next  home  signal.  He  must  confirm  this 
by  showing  him  a  green  flag  or  a  green  light,  and  then 
the  train  may  pass.  This  arrangement,  which  is  called 
the  "  permissive  block,"  is  impossible  with  "  lock  and 
block  "  instruments,  yet  without  it  some  of  the  great  north 

260 


How  Railways  are  Worked 

and'  south  lines,  for  instance,  could  not  cope  with  their 
enormous  goods  and  mineral  traffic. 

The  rules  for  block  working  have  something  to  say, 
too,  about  the  safety  of  trains  at  junctions.  I  used  to 
travel  to  London  every  day  by  the  London  and  South- 
western Railway,  and  at  Vauxhall  an  instance  of  this 
often  occurred.  Just  beyond  the  London  end  of  the 
platform  the  two  up  local  lines  converge  and  become 
one,  so  that  they  form  a  junction,  and  very  often  an 
up  local  train  would  stop  in  the  station  for  several 
minutes  for  no  apparent  reason.  Presently  another  train 
would  come  in  on  the  other  up  local  line,  and,  as  soon 
as  it  had  stopped,  the  first  train  would  start.  That  was 
because  of  a  rule  that  two  trains  must  not  approach  a 
junction  at  the  same  time.  Suppose  the  first  train  had 
started,  and  a  few  seconds  later  the  second  had  come 
in,  and  through  a  miscalculation,  or  through  slippery 
rails,  it  had  gone  a  few  yards  too  far,  it  would  have 
run  into  the  first  one  with  perhaps  serious  consequences. 
This  rule  is,  with  some  special  exceptions,  in  force  at 
all  junctions,  and  I  mention  it  for  this  reason.  I  have 
often  seen  a  train  stopped  under  these  conditions,  and 
instantly  there  have  been  heads  out  of  every  window 
trying  to  see  what  was  the  matter.  It  may  occur  the 
very  next  time  you  go  by  train,  and  it  will  then  be  of 
interest  perhaps  to  see  for  yourself  why  you  have  been 
stopped. 

So  much  for  the  methods  of  working  double  lines  of 
railway  ;  but  in  many  parts  of  England,  and  still  more 
abroad,  there  are  single  lines  where  the  trains  go  either 
way  over  the  same  metals.  If  it  is  a  short  branch,  it  is 
sometimes  worked  with  only  one  engine.  No  other 
engine  is  ever  allowed  on  the  line.  Then,  of  course, 
no  signalling  or  system  of  working  is  necessary. 

In  many  cases  the  line  is,  however,  of  considerable 
length,  and  sometimes  important  trains  pass  over  it. 

261 


How  Railways  are  Worked 

It  is  then  divided  up  into  sections,  and  at  the  end  of 
each  section  there  is  a  loop,  or  passing  place,  just  like 
what  we  often  see  on  tramways.  The  ordinary  block 
system  will  prevent  one  train  from  overtaking  another, 
but  what  is  to  prevent  two  trains  from  starting  from 
opposite  ends  of  a  section  at  the  same  time  and  colliding 
in  the  middle  ?  At  one  time  the  ordinary  telegraphic 
communication  was  thought  to  be  sufficient ;  but  the 
frailty  of  human  nature  came  in,  and,  through  a  mis- 
understanding between  two  signalmen,  a  terrible  collision 
occurred  on  a  single  line  near  Norwich. 

This  led  to  the  adoption  of  the  staff  system.  For 
each  section  there  was  a  staff,  a  sort  of  short  walking- 
stick  with  the  name  of  the  section  on  it,  and  no  driver 
was  allowed  to  enter  a  section  unless  he  had  the  proper 
staff  in  his  possession.  This  was  quite  safe,  but  it  had 
drawbacks.  Suppose  there  were  three  trains  all  waiting 
to  go  the  same  way,  and  none  ready  to  come  back  ? 
What  then  ?  The  first  train  might  go  with  the  staff, 
but  the  other  two  would  be  locked  up  for  some  time. 
This  difficulty  was  got  over  by  having  a  box  of  tickets 
at  each  end  which  the  staff  would  unlock — it  had  a 
piece  like  a  key  on  one  end  for  the  purpose.  A  signal- 
man could  then  show  the  driver  the  staff  but  not  give 
it  him,  handing  him  instead  one  of  these  tickets  giving 
him  permission  to  proceed.  So  the  first  and  second 
trains  could  go  with  tickets  and  the  third  take  the  staff. 

But  what  often  happened  was  this.  A  fourth  train 
turned  up  unexpectedly  after  the  third  had  gone,  and 
still  no  train  happened  to  be  coming  the  other  way  to 
bring  the  staff  back.  The  fourth  train  then  had  to  wait 
until  some  one  either  walked  or  came  on  horseback 
with  the  staff.  This,  of  course,  took  up  valuable  time, 
so  ultimately  the  tablet  system  was  invented  to  get 
over  the  trouble. 

In  this  there  is  an  electrical  apparatus  at  each  end 
262 


How  Railways  are  Worked 

of  the  section,  containing  a  number  of  tablets.  When 
a  train  is  ready  to  start  from  one  end  the  signalman 
takes  out  one  of  these  tablets  and  hands  it  to  the 
driver,  who  takes  it  as  his  permission  to  proceed  just 
as  in  the  case  of  a  staff.  But  the  action  of  taking  the 
one  tablet  out  locks  up  the  instruments  at  both  ends,  so 
that  it  is  impossible  for  either  signalman  to  obtain 
another  one.  As  soon  as  the  tablet  is  put  in  at  the 
other  end,  however,  it  unlocks  both,  so  that  if  there  is 
a  second  train  to  go  in  the  same  direction  a  second 
tablet  can  be  taken  out,  and  so  trains  could  keep  on 
going  in  the  same  direction  until  all  the  tablets  had 
been  used,  a  most  unlikely  thing  to  happen,  as  there 
are  a  lot  of  them.  All  the  same,  however,  as  only  one 
tablet  can  be  out  at  a  time  there  is  no  risk  of  a 
collision. 

Some  lines  use  what  is  called  the  electric-staff 
system  ;  but  it  is  practically  the  same  as  the  tablet 
system,  except  that  the  tokens,  instead  of  being  tablets, 
are  the  shape  of  the  old  staff. 

On  some  important  single  lines  there  are  devices  by 
the  side  of  the  line  to  enable  the  tablets  to  be  ex- 
changed without  the  train  having  to  stop,  and  in  some 
cases  it  is  arranged  to  have  a  master-tablet  for  through 
trains,  the  taking  out  of  which  locks  up  all  the  instru- 
ments all  along  the  line.  This  would,  of  course,  only 
be  used  for  important  trains. 


263 


CHAPTER   XX 

RAILWAY-SIGNALLING   MACHINERY 

IN  the  year  1908,  in  the  British  Isles,  1250  million 
people  travelled  by  train,  besides  season-ticketholders, 
yet  there  was  not  a  single  fatal  accident  to  a  passenger. 

This  fact  is  sufficient  to  justify  me  in  saying  that,  as 
far  as  safety  is  concerned,  the  art  of  railway  signalling 
has  almost  reached  perfection.  Signal  engineers  are 
therefore  devoting  a  good  deal  of  their  energies  now 
to  improvements  in  other  directions — such  as  reducing 
the  labour  employed,  or  increasing  the  capacity  of  the 
line  by  making  it  possible  to  get  more  trains  through 
in  a  given  time. 

With  these  ends  in  view  "  power  "  systems  are  being 
installed — systems  in  which  the  muscles  of  a  man's  arm 
are  replaced  by  electricity,  compressed  air,  or  some 
other  form  of  power.  In  most  cases,  although  a  man's 
muscles  can  be  dispensed  with,  his  brains  are  still 
required,  so  that  he  still  controls  the  signals  and  points 
by  means  of  handles  in  the  signal-cabin  although  the 
power  does  the  hard  work  for  him. 

On  lengths  of  line,  however,  where  there  are  no 
sidings  or  cross-overs,  but  where  the  traffic  is  all 
straightforward,  it  is  possible  to  do  without  signalmen 
altogether  and  make  the  trains  themselves  control  the 
signals  so  that  they  work  automatically. 

Parts  of  the  Metropolitan  District  Railway  (London), 
and  most  of  the  London  "  tubes  "  are  instances  of  this 
automatic  signalling,  and  on  the  former  some  of  my 

264 


Railway-Signalling  Machinery 

readers  have  probably  witnessed  the  passing  of  the 
signalman  and  the  actual  demolition  of  -the  cabins. 
Between  South  Kensington  and  Mansion  House,  for 
instance,  there  is  not  now  a  single  cabin  except  at 
St.  James's  Park,  where  there  is  one  which  is  opened 
if,  in  an  emergency,  they  need  to  use  the  cross-over 
road  there. 

The  line  is  divided  up  into  short  sections,  averaging 
about  900  feet  in  length,  and  there  is  a  signal  at  the 
commencement  of  each  section.  The  working  is  exactly 
like  a  man  entering  a  room  and  locking  the  door  be- 
hind him,  the  door  remaining  locked  until  he  has 
passed  out  of,  and  locked,  another  door  at  the  further 
end  of  the  apartment. 

The  signal  stands  normally  at  safety,  but,  as  soon  as 
a  train  passes  it,  it  goes  to  danger  and  remains  so  until 
the  train  has  passed  out  of  that  section  into  the  one 
beyond.  This  would  not  be  regarded  as  sufficient  on 
a  line  where  there  are  fast  trains.  On  such,  as  was 
explained  in  the  last  chapter,  there  are  always  two 
signals  protecting  a  train,  but  it  is  quite  safe  for  a  line 
like  the  District. 

The  system  on  which  these  lines  are  worked  is  called 
the  "Westinghouse  Electro-pneumatic/'the  signals  being 
worked  by  compressed  air  controlled  by  electricity. 
The  electricity  is  in  turn  controlled  by  the  train  itself, 
by  means  of  what  are  called  "  track  circuits,"  that  is  to 
say,  electrical  circuits  of  which  the  track — the  actual 
rails  on  which  the  trains  run — forms  a  part. 

One  of  the  rails  is  made  electrically  continuous 
throughout.  The  steel  plates  which  connect  the  lengths 
of  rail  together  (usually  called  "  fish  plates "),  being 
unfortunately  bad  electrical  connections,  are  supple- 
mented by  flexible  copper  "  bonds  "  which  carry  the 
current  from  one  piece  of  rail  to  the  next.  The  other 
rail  is  also  fitted  with  these  bonds,  but  instead  of  being 

265 


Railway-Signalling  Machinery 

electrically  continuous  throughout,  it  is  divided  up,  by 
special  insulating  joints,  into  lengths  which  correspond 
with  the  sections.  Each  of  these  lengths  of  rail  is 
connected  to  an  electric  cable. 

Current  from  a  dynamo  is  led  to  the  continuous 
rail,  and  from  there  it  goes  to  the  signal  and  holds  it 
at  safety.  From  the  signal  it  returns  to  the  divided 
rail,  and  then  goes  through  the  cable  back  to  the 
dynamo. 

As  soon  as  a  train  enters  a  section  it  "  short-circuits  " 
this  current,  provides  it,  that  is,  with  a  short  and  easy 
path  through  its  wheels  and  axles,  so  that  the  electricity 
can  get  from  the  continuous  rail  to  the  other  and  back 
to  the  dynamo  without  going  to  the  signal  at  all.  It 
therefore  deserts  the  signal  altogether,  and  permits  it 
to  go  to  danger  which  it  is  made  to  do  by  its  own 
weight. 

To  be  quite  accurate,  it  is  not  the  same  current  that 
flows  through  the  rail  which  works  the  signal,  although 
the  result  is  the  same  as  if  it  were.  The  former  goes 
to  an  instrument  called  a  "  relay/'  which  is  a  switch 
closed  by  an  electro-magnet,  but  opened  by  a  spring  or 
weight.  When  this  current,  which  is  a  weak  one, 
passes  through  the  coil  of  the  magnet,  it  closes  the 
switch  and  allows  the  stronger  current  to  flow  which 
works  the  signal ;  but  as  soon  as  the  weak  current 
ceases,  the  magnet  loses  its  power,  the  switch  springs 
open,  and  so  the  stronger  current  ceases  also. 

It  will  be  evident  that  this  is  a  very  safe  system,  as 
any  failure  of  the  air-pressure,  or  of  the  electricity,  only 
causes  the  signal  to  go  to  danger.  In  fact,  the  action 
by  which  the  train  puts  the  signal  at  danger  is  really 
an  artificial  failure  of  the  current. 

These  track  circuits  are  very  useful,  too,  in  connec- 
tion with  ordinary  hand-power  signalling  as  well  as 
with  automatic  and  power  systems.  For  instance,  if  a 

266 


Rail  way- Signalling  Machinery 

train  be  shunted  from  one  line  on  to  another,  to  allow 
something  to  pass,  it  is  possible  for  a  signalman  to 
forget  that  it  is  there  and  let  another  train  run  into 
it.  To  prevent  him  doing  so,  it  is  a  rule  that  under 
those  circumstances  the  guard  shall  go  to  the  signal- 
cabin  and  stay  there,  as  a  reminder,  until  the  train  has 
been  shunted  back  on  to  its  own  road  again.  If,  how- 
ever, it  were  standing  on  a  track  circuit,  it  could  be 
made  to  lock  the  signals  at  danger  and  so  protect  itself. 

But  that  is  by  the  way.  To  return  to  the  District 
Railway  :  the  pneumatic  motors  by  which  the  signal- 
arms  are  actually  lowered  are  small  cylinders  with  a 
piston  inside,  like  the  cylinders  of  a  steam-engine. 
The  air  comes  along  a  pipe  from  a  compressor,  and 
enters  the  cylinder  through  a  valve.  This  valve  is 
worked  by  an  electric  current  from  the  relay,  and  it  is 
so  made  that,  as  long  as  the  current  is  flowing,  the 
compressed  air  is  admitted  and  the  arm  held  down. 
As  soon  as  it  ceases  the  valve  moves,  shuts  off  the  air 
from  the  pipe,  and  lets  out  the  air  in  the  cylinder. 
Then  the  arm,  which  is  weighted  at  the  back  end,  flies 
to  danger  of  its  own  accord.  Thus,  as  I  said  just  now, 
any  failure  of  either  air  or  electricity  puts  the  signal  to 
danger. 

On  the  ground,  close  to  each  signal,  there  is  a  device 
by  which  the  brake  is  put  on  if  a  train  runs  past  it  at 
danger.  A  small  iron  arm  is  raised  when  the  signal  is 
up,  but  lowered  when  it  is  down,  being  operated  by 'a 
pneumatic  motor  just  as  the  signals  are.  When  this 
arm  is  up  it  strikes  against  a  projecting  lever  on  a 
passing  train,  and,  by  moving  it,  puts  the  brake  on. 

At  the  stations  where  there  are  junctions,  the  auto- 
matic system  is  impossible.  There  must  be  a  human 
brain  to  supervise  the  operations  ;  so  at  such  places  as 
Mansion  House,  South  Kensington,  and  Earl's  Court 
there  are  signal-cabins.  In  each  of  these  there  is  what 

267 


Railway-Signalling  Machinery 

looks  like  a  large  dwarf  book-case,  with  a  row  of 
handles  along  the  top.  These  are  the  handles  of 
switches  by  which  the  signalman  can  send  an  electric 
current,  or  stop  it,  as  may  be  necessary.  Thus  he 
operates  the  signals  just  as  the  relay  does  on  the 
automatic  sections. 

The  working  of  the  points  is  a  little  different,  because 
they  need  to  be  forced  sometimes  in  one  direction  and 
sometimes  in  another.  The  motors  are,  therefore, 
double-acting — the  air  pushes  the  piston  one  way  when 
the  electricity  is  flowing,  and  the  other  way  when  it 
stops. 

In  each  of  the  cabins  there  is  an  illuminated  diagram. 
A  plan  of  all  the  lines  in  the  station,  and  some  distance 
on  each  side  of  it,  is  drawn  upon  glass.  Behind  the 
glass  are  electric  lamps  arranged  to  work  in  connection 
with  ^the  relays.  Normally  the  whole  is  illuminated, 
but,  as  soon  as  a  train  enters  a  section,  that  section  (on 
the  plan)  becomes  dark.  The  signalman  can  thus  see 
at  a  glance  the  position  of  the  approaching  and  receding 
trains. 

Inside  the  "  bookcase,"  as  I  have  called  it,  is  an 
arrangement  whereby  the  handles  above  are  all  inter- 
locked just  as  the  ordinary  levers  are  interlocked  in  a 
hand-worked  system. 

In  America,  where  automatic  signalling  originated, 
and  where  it  is  much  more  largely  used  than  it  is  any- 
where else,  one  of  the  principal  reasons  for  its  adoption 
was  that  the  lines  often  traverse  wild,  uncivilised  districts, 
where  no  signalman  could  be  induced  to  live. 

The  chief  advantage  of  an  automatic  system  in  England 
is  economy.  To  take  the  "  District "  as  an  example,  in 
order  to  increase  the  number  of  trains  it  was  necessary 
to  reduce  the  length  (and  increase  the  number)  of  the 
sections.  This  under  the  old  system  would  have  meant 
building  a  large  number  of  new  cabins  and  employing 

268 


Railway-Signalling  Machinery 

more  signalmen  ;  but,  with  automatic  signals,  to  divide 
a  section  into  two  only  means  an  extra  signal  and  a 
set  of  relays. 

On  the  North-Eastern  Railway  of  England,  and  in 
several  places  in  the  United  States,  there  is  an  interest- 
ing system  in  use  called  the  "  Hall  Electric-gas  System." 
The  train  controls  the  signals  automatically  by  electric 
track-circuits  something  similar  to  the  District  method, 
but,  instead  of  compressed  air,  compressed  carbonic- 
acid  gas  is  used  to  supply  the  motive  power.  This 
saves  the  cost  of  the  piping,  because  the  compressed  gas 
can  be  stored  in  a  cylinder  at  the  foot  of  each  signal 
post.  The  gas  is  compressed  to  900  Ibs.  per  square 
inch,  at  which  pressure  it  is  liquid,  and  it  is  liberated 
through  a  valve  which  lets  the  pressure  down  gradually 
to  40  Ibs.  per  square  inch  before  it  enters  the  cylinder 
of  the  motor.  If  it  were  admitted  direct  from  the 
storage-cylinder  to  the  motor,  the  sudden  expansion 
would  cause  it  to  freeze. 

Incidentally,  this  illustrates  the  interesting  scientific 
fact  that  matter  may  take  three  different  forms.  Car- 
bonic acid  is  under  ordinary  conditions  a  gas  ;  indeed, 
we  manufacture  it  in  our  lungs  and  exhale  it  every  time 
we  breathe.  If  we  compress  it,  however,  as  we  have 
just  seen,  it  becomes  liquid,  and  if  we  subject  that  liquid 
to  a  certain  degree  of  cold,  it  freezes  and  becomes 
solid. 

There  is  enough  gas  in  one  cylinder  for  12,500 
operations,  and  two  cylinders  are  placed  at  each  post,  so 
that  if  one  runs  out  the  other  can  be  connected  up 
immediately.  Periodically  the  empty  ones  are  all  taken 
away  and  full  ones  put  in  their  place. 

The  London  and  South- Western  Railway  (England) 
have  adopted  at  several  places  along  their  line  the  "  low- 
pressure  pneumatic"  system.  In  this  everything  is 
done  by  compressed  air,  the  motors  for  the  signals  and 

269 


Rail  way- Signal]  ing  Machinery 

points  being  worked  by  a  pressure  of  15  Ibs.  per 
square  inch,  and  the  valves  by  a  pressure  of  7  Ibs. 
This  is  tl  low "  in  comparison  with  the  Westinghouse 
system,  which  uses  air  at  65  to  70  Ibs.  pressure. 

A  great  number  of  pipes  are  needed — four  for  each 
set  of  points,  and  three  for  each  signal — to  convey  the 
air  from  the  cabin  to  the  motors.  The  points  and 
signals  are  worked  by  the  movement  of  small  handles 
in  the  signal-cabins,  which  when  pulled  admit  air  to 
the  pipes,  and  these  handles  are  interlocked.  All  the 
signals  go  to  danger  automatically  when  a  train  passes, 
and  on  some  parts  of  the  line  they  work  entirely  auto- 
matically— the  train  controls  them  by  track-circuits,  as 
in  the  Westinghouse  system. 

On  the  London  and  North-Western  Railway  at 
Crewe  and  Euston  (England),  and  on  the  North- 
Eastern  Railway  at  York  (England),  there  is  an  all- 
electric  system  called  the  "  Crewe "  system.  It  was 
devised  by  Mr.  Webb,  for  many  years  the  chief 
mechanical  engineer  on  the  London  and  North-Western 
Railway.  Switches  in  the  cabin  permit  currents  of 
electricity  to  pass  to  the  signals  or  points,  as  the 
case  may  be.  The  points  are  worked  by  electric 
motors  placed  on  the  line  close  to  them,  and  the 
signals  by  electro-magnets. 

Another  all-electric  system  (the  Siemens)  has  been 
tried  on  the  Midland  Railway  and  the  Great  Western 
Railway,  and  is  now  being  installed  on  a  large  scale  at 
Snow  Hill,  Birmingham  (England).  This  system  is 
largely  used  on  the  continent  of  Europe. 

Signal  engineers  have  a  curious  way  of  calling  hand- 
power  systems  "  mechanical "  as  opposed  to  "  power  " 
systems.  It  is  strange,  seeing  that  there  is  far  more 
mechanism  in  the  latter  than  in  the  former.  The 
"  half-and-half "  system  in- use  at  St.  Enoch's  Station, 
Glasgow  (Scotland),  and  at  Victoria  Station,  London 

270 


Railway-Signalling  Machinery 

(London,  Brighton,  and  South-Coast  Railway),  is  there- 
fore called  "  electro-mechanical." 

In  this  there  are  the  usual  large  levers  for  working 
the  points,  and  the  signalman  pulls  them  over  by  hand. 
Above  them,  on  the  edge  of  the  shelf  on  which  the 
block-telegraph  instruments  stand,  there  is  a  row  of 
small  handles,  and  through  these  the  signals  are  worked 
by  electricity.  There  is  a  small  electro-motor  on  each 
signal-post,  by  which  the  arm  is  pulled  down.  It 
remains  down  as  long  as  the  current  is  flowing,  but 
flies  to  danger  as  soon  as  it  stops.  Of  course  the 
handles  and  levers  are  all  interlocked. 

There  are  also  hydraulic  systems,  but  they  are  not 
much  used  in  cold  countries  owing  to  the  liability  of 
the  water  to  freeze. 

Probably  a  good  many  readers  will  at  this  point  be 
inclined  to  remark,  "  I  see  the  advantage  of  an  auto- 
matic system,  but  what  is  the  advantage  of  a  power 
system  which  is  not  automatic  ?  " 

In  the  first  place,  the  men  are  relieved  of  much  hard 
work.  Then  it  is  easy  to  arrange  in  a  power  system 
that  every  movement  of  a  signal  or  point  shall  be 
repeated  back  to  the  signal  cabin  by  a  return  current, 
so  that  when  a  lever  or  handle  has  been  moved,  the 
next  one  cannot  be  pulled  until  the  "  return  "  has  come 
which  indicates  that  the  points  or  signal  have  properly 
responded  to  the  movement.  This  is  very  safe,  but  it 
is  not  so  great  an  advantage  as  it  at  first  appears  to  be, 
since  even  in  a  mechanical  system  there  is  something 
of  the  sort,  for  an  experienced  signalman  can  tell  a 
good  deal  by  the  "  feel  "  of  his  lever  when  he  pulls  it. 

Then  the  cabins  can  be  very  much  smaller  with  a 
power  system,  as  the  small  levers  or  handles  take  up 
much  less  room  than  the  large  levers  used  in  mechanical 
systems.  Points  and  signals  can  be  operated,  too,  at  a 
much  greater  distance  from  the  cabin,  so  that  fewer 

271 


Railway-Signalling  Machinery 

cabins  are  needed.  A  striking  instance  of  this  is  at 
Staines  (England),  on  the  London  and  South-Western 
Railway,  where  two  "  power  "  cabins  now  do  the  work 
that  used  to  require  five. 

It  is  hardly  necessary  to  refer  in  detail  to  the  me- 
chanical signalling  which  is  in  operation  in  the  majority 
of  cabins.  The  long  row  of  levers  is  familiar  to  every 
one.  Each  of  these  is  connected  to  a  signal  or  set  of 
points,  to  the  former  by  a  wire  and  to  the  latter  by  a 
rod,  the  interlocking  apparatus  being  under  the  floor. 

I  will  therefore  pass  on  to  the  second  part  of  the 
chapter,  which  I  think  is  sufficiently  important  to  have 
a  sub-heading.  I  propose  to  call  it 

How  TO  READ  SIGNALS 

In  this  I  will  try  to  describe  briefly  the  "  visible " 
part  of  the  signalling  machinery — the  part  by  which 
the  driver  gets  his  instructions — and  I  venture  to 
think  that  this  will  interest  many  of  my  readers,  as  it 
relieves  the  tedium  of  a  wait  at  a  station,  and  adds 
much  to  the  interest  of  a  journey  if  one  can  understand 
something  of  the  signals. 

As  I  explained  in  the  last  chapter,  there  is  at  every 
station,  for  each  line,  a  home  signal  and  a  starting 
signal — the  former  at  the  side  from  which  the  train 
approaches,  and  the' latter  at  the  other  side,  the  platform 
being  between  them.  Then  about  1000  yards  back 
there  is  a  distant  signal.  This  is  distinguished  by 
having  a  V-shaped  piece  cut  out  of  the  end  of  the  arm, 
and  its  purpose  is  to  indicate  to  a  driver  how  the  home 
signal  stands.  If  it  is  at  danger,  therefore,  a  train  does 
not  stop,  but  slackens  speed,  so  as  to  be  able  to  stop  if 
necessary  at  the  home  signal. 

Sometimes  a  tall  signal  has  a  second  arm,  slightly 
smaller  than  the  other  one,  and  comparatively  near  the 
ground.  This  is  a  repeater,  which  goes  up  and  down  with 
the  upper  arm,  and  is  used  at  places  where  something, 

272 


Railway-Signalling  Machinery 


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such  as  a  bridge,  obscures  the  driver's  view  of  the  upper 
arm  when  the  train  is  in  certain  positions.  The  very  small 
arms  sometimes  seen  close  to  the  ground  are  "  fogging  " 
arms,  and  are  for  the  information  of  the  men  who  put 
the  fog-signals  down  on  the  line  in  foggy  weather. 

The  signals  which  control  shunting  operations  are 
generally  near  the  ground,  and  very  often  take  the  shape 
of  discs,  which  do  not  go  up  and  down,  but  turn  round 
a  quarter  of  a  circle.  These  are  called  ground  discs. 

At  large  stations  there  is  often  a  small  arm  to  be 
seen,  just  under  the  ordinary  signal  arm.  This  is 
known  as  a  "calling-on"  arm,  or  "  draw-ahead"  signal, 
and  its  purpose  is  to  give  permission  to  a  driver  to  go 
on  although  the  large  signal  is  at  danger.  This  seems 
a  dangerous  and  improper  proceeding,  but  it  is  both 
necessary  and  safe  under  conditions  like  these.  In 
many  large  stations  the  platforms  are  long  enough  for 
two  trains,  the  first  of  which  can  be  signalled  in,  in  the 
ordinary  way,  after  which  the  large  signal  must  be  kept 
at  danger  in  order  to  protect  it.  Another  train  may  then 
approach  which  has  passengers  wishing  to  change  into  the 
first,  so  that  it  must  be  admitted  into  the  station  at  once. 
It  is  therefore  stopped  dead  by  the  ordinary  signal,  and 
then  the  small  arm  is  lowered,  by  which  the  driver  knows 
that  he  is  to  draw  gently  up  to  the  other  train. 

If  the  station  is  a  terminus,  there  is  generally  another 
small  arm  under  the  "  calling-on  "  arm.  It  is  usually 
distinguished  by  being  of  some  peculiar  shape,  and  it 
is  used  to  let  in  the  engine  which  is  going  to  fetch  the 
train  out  again. 

Signals  may  often  be  met  with  where  the  arm  has  a 
large  ring  fixed  on  it.  These  relate  to  goods  or  "  slow  " 
lines,  and  are  so  marked  to  enable  them  to  be  easily 
distinguished  from  the  others.  For  the  same  reason 
shunting-signals  (when  placed  on  a  post)  sometimes 
have  a  letter  S  fixed  on  the  end  of  the  arm.  A  cross 
on  the  end  of  an  arm  indicates  that  it  is  out  of  use. 

274 


Railway- Signalling  Machinery 

As  far  as  possible  signals  are  placed  close  to  the 
lines  to  which  they  refer,  but  when  there  are  several 
lines  in  the  same  direction  this  is  not  always  possible. 
Sometimes  they  are  then  placed  on  a  bridge,  each  signal 
over  its  own  line,  but  very  often  they  are  put  one 
above  another  on  the  same  post.  The  top  one  then 
refers  to  the  line  on  the  extreme  left ;  the  next  one  to 
the  left  but  one  ;  and  so  on  if  there  are  more  than  two. 
This  is  not  allowed,  however,  to  interfere  with  the 
almost  invariable  rule  that  a  signal  for  the  main  line 
must  be  the  highest  of  all,  so  that  if  the  main  line  is 
not  on  the  left,  the  main  line  signal  has  a  post  to  itself 
higher  than  the  other  ones. 

As  regards  the  lights  for  showing  signals  at  night, 
the  usual  rule  is  red  for  danger,  and  green  for  safety  ; 
but  sometimes,  on  signals  of  minor  importance,  the 
danger-light  is  now  purple,  so  as  to  avoid  the  confusion 
that  might  result  from  having  too  many  red  lights. 
The  danger-lights  on  shunting-signals  are  sometimes 
white,  which  may  seem  surprising,  but  it  is  now  an  in- 
variable rule  that  a  white  light  is  a  danger  signal,  since 
if  it  were  not  so  a  street  lamp  or  a  light  in  a  window 
might  be  mistaken  for  a  safety  signal,  or  a  well-directed 
stone  from  a  small  boy  might,  by  knocking  out  the  red 
glass,  make  a  signal  stand  permanently  at  safety.  A 
"calling-on  "  signal  shows  a  green  light  for  safety,  but 
nothing  at  all  when  at  danger. 

On  some  lines  now  a  distant-signal  is  distinguished 
by  a  special  lamp  which  shows  a  strip  of  light  the 
shape  of  the  stripe  on  the  arm  of  a  lance-corporal,  in 
addition  to  the  ordinary  "  Bull's  Eye." 

The  small  light  shown  at  the  back  of  a  signal  lamp 
is  to  enable  the  signalman  to  see  that  the  light  is 
burning  properly,  and  that  the  arm  goes  properly  to 
danger.  It  is  unnecessary  when  he  can  see  the  front 
of  the  signal.  These  lights  are  white  when  at  danger, 
but  obscured  when  at  safety. 

275 


CHAPTER    XXI 

THE   MANUFACTURE   OF   GAS 

IN  spite  of  the  many  advantages  of  Electric  Light,  gas 
manufacture  is  still  an  important  and  thriving  industry. 
This  is,  no  doubt,  largely  owing  to  the  introduction 
of  the  incandescent  mantle,  and  the  ever-increasing  use 
of  gas  for  heating  purposes.  In  Great  Britain  alone 
about  14,000,000  tons  of  coal  are  used  annually  for 
making  gas. 

The  general  principles  of  the  manufacture  of  coal- 
gas  are  well  known.  Suitable  coal  is  heated  to  about 
2000°  Fahr.  in  fire-clay  retorts  for  a  period  of  six  to 
twelve  hours,  and  as  the  result  gas  is  given  off,  which 
subsequently  undergoes  certain  purifying  processes, 
while  coke  is  left  in  the  retorts.  So  far  the  matter  is 
familiar  and  commonplace,  but  when  we  see  how  it  is 
done  on  an  enormous  scale  it  becomes  very  inter- 
esting. 

First  of  all  let  us  visit  the  Retort  House  of  a  large 
works.  It  is  a  huge  plain  building  of  two  storeys,  about 
50  feet  wide,  and  of  a  length  which  varies  according 
to  the  size  of  the  works.  Down  the  centre  runs  a 
rectangular  brick  structure,  with  a  flat  top,  nearly  as 
high  as  the  roof  of  the  house.  This  is  the  furnace 
which  contains  the  retorts. 

The  latter  are  thick  strong  pipes  of  fire-clay,  either 
oval,  round,  or  else  resembling  a  capital  letter  D  in 
shape.  They  are  about  18  feet  long,  and  run  right 
through  the  furnace  from  side  to  side,  being  closed  at 
each  end  with  an  iron  lid. 

276 


The  Manufacture  of  Gas 

They  are  placed  in  groups  of  from  six  to  ten,  each 
of  the  groups  being  termed  a  "  bench  "  of  retorts,  and 
a  large  house  will  contain  as  many  as  twenty  or  thirty 
benches,  or  200  to  300  retorts.  Just  behind  the  iron 
lid  there  is  an  outlet,  from  which  a  pipe  called  the 
"  ascension  pipe "  runs  vertically  upwards,  like  the 
pipes  of  an  enormous  organ. 

The  retorts  are  not  generally  heated  by  the  direct 
heat  of  a  fire  but  by  producer  gas.  As  explained  in 
the  chapter  on  Gas-Engines,  if  air  be  drawn  through 
a  deep  coke  fire,  closed  at  the  top,  the  process  of  burning 
only  takes  place  at  the  bottom  of  the  fire,  the  fuel 
above  it  being  simply  heated  to  incandescence ;  the 
consequence  of  which  is  that  the  carbonic-acid  gas, 
the  incombustible  gas  which  results  from  burning,  is 
converted,  in  passing  upwards,  into  carbonic-oxide  or 
carbon-monoxide,  a  gas  which  burns  with  great  heat. 

Beneath  the  retorts,  therefore,  a  Gas  Producer  is 
placed — simply  a  large  deep  furnace,  the  gas  from 
which  is  led  up  brick  passages  to  combustion-chambers 
formed  in  the  brickwork  amongst  the  retorts.  At  the 
same  time  fresh  air,  called  in  the  gas-works  "  second- 
ary air,"  is  drawn  into  the  combustion-chambers,  and 
as  soon  as  the  gas  and  air  mingle  they  burst  into  flame. 
The  flames  then  pass  through  passages  amongst  and 
around  the  retorts,  finally  escaping  to  the  chimney 
stack.  The  secondary  air  on  its  way  to  the  combus- 
tion-chamber passes  through  passages  formed  in  the 
brickwork  around  the  retorts,  so  that  it  intercepts  and 
carries  back  some  of  the  heat  which  would  otherwise 
escape  into  the  atmosphere.  The  tf  secondary  "  air  is  so 
called  to  distinguish  it  from  the  "  primary  "  air,  which 
is  that  drawn  in  at  the  bottom  of  the  producer.  There 
is  usually  one  producer  for  several  benches  of  retorts.1 

1  It  will  be  noticed  that  the  heating  of  gas-retorts  by  producer  gas  is  very 
similar  to  the  method  of  heating  a  Siemens  Steel  Furnace,  described  in  an 
earlier  chapter. 

277 


The  Manufacture  of  Gas 

I  have  stated  already  that  the  Retort  House  is  about 
50  feet  wide,  while  the  retorts  themselves  are  under 
20  feet  long,  so  that  between  the  furnace  and  the  wall 
on  either  side  there  is  a  wide  passage  way.  Here,  on 
the  first  floor,  there  are  rails  on  which  run  two  large 
machines,  one  a  "  charging  machine  "  and  the  other  a 
"  coke-discharging  "  machine. 

In  the  top  of  the  charging  machine  is  a  hopper  con- 
taining coal,  and  in  the  front  of  it  a  spout  which  just 
fits  nicely  into  the  mouth  of  the  retort.  The  machine 
places  itself  in  front  of  the  retort  to  be  filled,  and 
pushes  the  spout  just  into  its  mouth ;  then  a  ram  starts 
to  move  backward  and  forward,  at  each  forward  stroke 
pushing  a  quantity  of  coal  into  the  retort,  until  it  is 
half  full.  At  the  same  time,  a  similar  machine  at  the 
other  side  of  the  house  has  been  doing  the  same  thing 
through  the  opposite  end  of  the  retort,  so  that  between 
them  they  fill  it  quite  full.  Then  they  withdraw  their 
spouts,  the  doors  are  closed,  and  the  coal  is  left  to 
bake. 

The  coke  discharger  may  be  either  a  "  pusher  "  or  a 
drawing  machine.  Both  are  somewhat  similar  at  first 
sight  to  the  "  charger." 

A  pusher  has  a  long  arm  consisting  of  tubes  sliding 
one  in  another  like  a  telescope,  and  on  the  end  of  it  is 
a  rammer,  the  shape  of,  and  almost  filling  the  retort. 
When  all  the  gas  has  been  obtained  from  the  coal 
the  doors  are  opened  at  both  ends,  the  machine  inserts 
its  rammer  and  pushes  the  whole  of  the  coke  right 
out  through  the  opposite  end. 

A  "  drawing  machine,"  on  the  other  hand,  has  an  arm 
like  a  rake,  which  it  inserts  into  the  retort,  and  with 
which  it  draws  the  coke  out.  These  machines  work 
by  hydraulic  power,  and  the  speed  with  which  they 
do  their  work  is  truly  remarkable. 

Two  charging  machines  working  together  can  fill 

278 


The  Manufacture  of  Gas 

a  retort  with  9  cwt.  of  coal  every  45  seconds,  that 
interval,  of  course,  including  the  time  taken  in  moving 
from  one  retort  to  the  next.  The  coke-discharger  can 
work  even  more  quickly. 

There  are  similar  machines  worked  by  electric, 
pneumatic,  and  (for  small  works)  by  hand  power. 

The  gas,  as  it  is  given  off  by  the  coal,  escapes  up 
the  "  ascension  pipes."  These  bend  over  and  dip  down 
into  a  large  pipe  called  the  "  hydraulic  main,"  which 
runs  along  the  top  of  the  furnace.  This  pipe  is  half 
full  of  water,  or  rather  "  liquor,"  as  it  is  called,  the 
nature  of  which  we  shall  see  presently,  and  the  out- 
lets from  the  ascension  pipes  dip  down  into  this  liquid. 
This  forms  a  "  liquor  seal  " — gas  coming  from  the 
retorts  can  bubble  up  through  it,  but  no  gas  can  get 
back,  as  it  might  otherwise  do,  when  the  retort  lids  are 
opened. 

From  the  hydraulic  main  the  gas  passes  to  the 
"  foul  main,"  which  leads  it  to  the  condenser. 

Now,  any  one  who  has  tried  the  little  experiment 
beloved  of  boys  of  making  gas  in  a  "  churchwarden  " 
pipe,  will  have  noticed  that  it  is  smoky  in  appear- 
ance. That  is  because  of  the  steam  and  tarry  vapour 
which  must  be  got  rid  of  before  the  gas  can  be  sent 
out  through  the  mains.  This  clearing  process  takes 
place  to  a  certain  extent  in  the  hydraulic  main  and 
foul  main,  but  it  commences  in  earnest  in  the  con- 
denser. 

In  old  works,  this  simply  consists  of  a  zig-zag  pipe 
fixed  to  the  outer  wall  of  the  Retort  House,  and  cooled 
by  contact  with  the  air.  Through  this  the  gas  slowly 
passes,  being  cooled  as  it  goes,  a  good  deal  of  the 
vapour  being  condensed  into  liquid  tar,  which  runs 
down  and  is  drawn  off  through  a  valve  at  the  bottom. 
In  a  modern  works,  however,  the  gas  passes  through 
pipes  which  are  kept  cool  by  water  circulating  round 

279 


The  Manufacture   of  Gas 

them,  just  like  a  surface-condenser  in  a  steam-engine 
plant. 

Thence  it  goes  to  the  "  washer,"  where  it  is  forced 
through  little  metal  tunnels  with  holes  in  the  bottom, 
partly  immersed  in  water.  Out  of  these  holes  it  has 
to  find  its  way,  the  tiny  globules  of  tar  which  form  the 
vapour  being  broken  and  liquefied  as  it  does  so  ;  and 
as  the  holes  are  under  water,  it  must  needs  at  the  same 
time  bubble  up  through  it,  giving  up  to  the  water  some 
of  the  ammonia  which  it  contains.  Here  the  last 
vestige  of  tar  is  removed. 

The  gas  still  contains  impurities,  however,  the  prin- 
cipal ones  being  ammonia  and  sulphuretted  hydrogen, 
which  must  somehow  be  got  rid  of.  The  first,  fortu- 
nately, has  a  great  liking  for  water,  so  the  gas  is  made 
to  travel  up  a  high  tower  called  a  "  scrubber,"  passing 
among  layers  of  wet  boards  set  on  edge,  and  meeting 
a  spray  of  water  falling  from  the  top.  In  many  works, 
too,  it  goes  through  a  rotary  washer,  in  which  revolving 
steel  brushes  throw  a  spray  of  water  through  which  the 
gas  has  to  pass. 

Finally,  in  the  "purifiers,"  it  percolates  through 
layers  of  iron  oxide,  which  absorb  the  sulphuretted 
hydrogen,  and  it  is  then  ready  to  go  to  the  gas-holder. 

Of  course,  the  gas  will  not  pass  through  all  these 
different  appliances  of  its  own  accord,  since  they  all 
offer  some  slight  resistance  to  its  passage.  At  one 
point  in  the  series,  therefore,  such  as  between  the 
condenser  and  the  washer,  there  is  a  pump  called 
the  Exhauster,  driven  by  a  steam-engine,  which  acts 
like  the  heart  of  the  system,  and  keeps  up  a  regular 
circulation. 

Most  works,  both  large  and  small,  use  horizontal 
retorts  as  described  above  ;  but,  in  some,  inclined  or 
vertical  retorts  are  used.  These  are  more  easily 
charged,  of  course,  because  the  coal  will  fall  into  them, 

280 


The  Manufacture   of  Gas 

and  does  not  need  to  be  pushed  in.  In  the  same  way, 
the  coke  will  fall  out.  In  some  of  them  the  process 
of  gas-making  is  made  continuous  instead  of  inter- 
mittent, the  coal  being  fed  in  in  small  quantities  at  the 
top,  at  frequent  intervals,  and  the  coke  being  taken  out 
in  the  same  way  at  the  bottom.  The  relative  advantages 
of  the  different  types  of  retort  is  a  subject  of  much 
discussion  among  gas  engineers. 

The  introduction  of  the  vertical  retort  has,  how- 
ever, had  a  more  important  effect  indirectly,  than  it 
has  had  up  to  the  present,  directly,  for  it  has  revolu- 
tionised the  methods  of  working  in  many  works  equipped 
with  horizontal  retorts. 

It  is  desirable  to  get  the  gas  out  of  the  retort  as 
quickly  as  possible  after  it  has  been  given  off,  for  if  it 
remains  in  contact  with  the  hot  coke  it  becomes  im- 
poverished. For  this  reason  it  used  to  be  the  custom 
to  fill  the  retort  only  about  two-thirds  full ;  a  layer  of 
coal,  that  is,  was  spread  on  the  bottom  so  as  to  leave 
a  clear  passage  above  for  the  gas  to  reach  the  ascension 
pipe.  To  accomplish  this,  the  coal  was  fed  in  with  a 
long  scoop,  which  was  pushed  right  in,  and  then  turned 
over,  so  as  to  have  the  coal  evenly  spread  upon  the 
floor  of  the  retort,  a  plan  which  is  still  in  use  in  small 
works.  It  is  quite  evident,  however,  that  it  would  not 
work  in  a  vertical  retort,  for  the  weight  of  the  coal 
would  cause  it  to  fill  the  retort  entirely,  and  leave  no 
passage  for  the  gas  ;  and  the  fact  that  vertical  retorts 
gave  a  satisfactory  result  opened  the  eyes  of  the 
engineers  to  the  fact  that,  at  any  rate  in  large  works 
where  they  use  charging  machines,  they  might  as  well 
fill  their  horizontal  retorts  right  up,  thereby  effecting 
an  enormous  saving  in  labour. 

Under  the  old  system,  the  men  worked  in  three 
shifts  of  eight  hours  each.  During  a  shift,  they  dis- 
charged and  charged  each  retort  once.  An  1 8-foot 

281 


The  Manufacture  of  Gas 

retort  under  those  circumstances  was  filled  with  about 
6  cwt.  of  coal,  which  it  gasified  in  eight  hours.  Under 
the  new  system,  9  cwt.  of  coal  is  put  in  and  left  for 
twelve  hours.  The  men  can  do  the  work  of  charging 
and  discharging  in  the  same  time  as  before,  after  which 
the  retorts  are  left  practically  to  themselves  for  four 
hours.  Thus  two  shifts  per  day  of  eight  hours,  with 
four-hour  intervals  between,  can  make  as  much  gas  as 
three  shifts,  working  continuously,  used  to  do  under 
the  old  system. 

So  much  for  coal-gas.  Now  we  can  turn  our 
attention  to  "  carburetted  water-gas,"  which  is  often 
used  to  enrich  it ;  that  is  to  say,  increase  its  light-giving 
power,  and  sometimes,  even,  instead  of  it. 

The  two  gases  are  really  very  similar  in  composition. 
They  are  both  only  " gases"  in  the  commercial  sense 
of  the  term,  being  mixtures  of  several  gases  as  known 
to  the  chemist.  These  constituent  gases  are  much  the 
same  in  both  cases,  the  difference  between  the  two 
mixtures  lying  mainly  in  the  proportions. 

Speaking  roughly,  the  principal  constituents  of  coal- 
gas  are  hydrogen  (about  50  per  cent.),  methane,  a  com- 
bination (not  a  mixture,  mind)  of  carbon  and  hydrogen 
(over  30  per  cent.)  and  nearly  10  per  cent,  of  carbon- 
monoxide.  These  three  gases  make  up  about  nine- 
tenths  of  the  whole.  The  precise  composition  varies 
in  different  towns. 

The  same  three  gases  make  up  four-fifths  of  car- 
buretted water-gas,  but  instead  of  the  carbon-mon- 
oxide being  under  one-tenth  of  the  whole,  it  forms 
nearly  one  quarter,  resulting  in  more  perfect  com- 
bustion, so  that  this  gas  gives  a  more  brilliant  flame 
than  does  coal-gas,  and  by  adding  it  to  the  latter  a 
greater  illuminating  power  is  produced. 

The  plant  for  making  carburetted  water-gas  is  quite 
different  from  that  for  making  coal-gas.  The  part 

282 


The  Manufacture  of  Gas 

where  the  gas  is  actually  made,  which  corresponds,  in 
fact,  to  the  bench  of  retorts,  consists  of  three  cylin- 
drical steel  vessels,  lined  with  fire-bricks.  The  first  of 
these  is  called  the  generator,  the  next  the  carburettor, 
and  the  third  the  superheater. 

The  generator  is  really  a  furnace,  with  a  grate  at  the 
bottom.  It  is  filled  with  coke  and  ignited,  and  the  fire 
is  then  urged  by  means  of  a  blast  of  air  from  a  fan. 
Except  for  a  door,  through  which  the  coke  is  fed  in, 
the  top  of  the  generator  is  closed,  so  the  hot  gases  from 
the  fire  have  to  pass  through  a  short  pipe  into  the 
carburettor.  This  is  filled  with  loosely-stacked  bricks, 
like  the  regenerating  chambers  in  a  Siemens  Steel 
Furnace,  and  these  become  heated  by  the  hot  gases. 
The  latter  then  pass  on  to  the  superheater,  which  is 
also  filled  with  bricks,  after  heating  which  they  escape 
up  a  chimney.  After  this  preliminary  process — which 
is  spoken  of  as  "  the  blow  " — has  been  going  on  for  a 
little  while,  there  is  in  the  generator  a  mass  of  in- 
candescent coke  and  in  the  carburettor  and  superheater 
masses  of  hot  bricks.  Then  all  is  ready  for  the  "  run," 
or  actual  gas-making  part  of  the  proceedings. 

The  blast  is  shut  off,  and  a  jet  of  steam  from  a 
boiler  introduced  instead.  Now  we  saw  when  discuss- 
ing the  subject  of  gas-engines  that  steam  in  passing 
through  incandescent  carbon  becomes  split  up  and 
forms  hydrogen  and  carbon-monoxide.  Consequently 
there  issues  from  the  generator  into  the  carburettor  a 
volume  of  these  two  gases.  Entering  the  carburettor 
they  encounter  a  fine  spray  of  oil,  the  gas  and  oil 
spray  passing  down  together  through  the  hot  bricks, 
the  oil  being  thereby  vapourised  and  mixed  with  the 
gas.  Then  to  ensure  that  these  processes  shall  be 
complete,  the  stream  flows  on  through  the  further 
mass  of  hot  bricks  in  the  superheater,  after  which  the 
gas  may  be  regarded  as  made. 

283 


The   Manufacture  of  Gas 

After  leaving  the  superheater  the  gas  goes  through 
an  "  oil-heater,"  where  some  of  its  heat  is  utilised  to 
heat  the  oil  for  use  in  the  carburettor  ;  then  it  passes 
via  a  washer,  scrubber,  and  condenser  to  the  holder. 

When  the  "  run "  has  been  continued  for  a  little 
time  the  generator,  carburettor,  and  superheater  begin 
to  get  too  cold,  so  the  steam  is  then  shut  off  and  the 
heat  got  up  again  by  another  "  blow."  So  the  process 
goes  on,  run  and  blow  alternately. 

In  addition  to  the  advantages  which  the  gas  itself 
possesses,  the  plant  has  valuable  qualities  of  its  own. 

Suppose  a  spell  of  foggy  weather  should  set  in,  the 
demands  on  the  gas-works  are  very  heavy.  The  spare 
retorts  are  unable  to  respond  to  this,  for  it  takes  at  least 
three  days  to  get  the  heat  up,  and  even  then  the  stresses 
due  to  expansion  and  contraction  are  so  severe  as  to 
be  liable  to  damage  the  retorts  and  their  settings.  It 
is  much  better,  therefore,  to  get  up  the  heat  more 
gently,  and  take  a  fortnight  over  it. 

The  consequence  of  this  is  that  sufficient  gas  must  be 
kept  stored  in  the  gas-holders,  to  provide  against  an 
unexpected  demand. 

On  the  other  hand,  the  water-gas  plant  can  be  going 
full  swing  in  three  hours  from  the  lighting  of  the  fires. 
Moreover,  it  sometimes  happens  that  the  quality  of  the 
coal-gas  produced  in  a  works  falls  off  for  some  reason — 
such,  for  example,  as  a  cargo  of  bad  coal — but  when 
carburetted  water-gas  is  used  for  enriching  it  this  can 
be  rectified  by  simply  increasing  the  quantity  of  oil 
used. 

The  oil,  by  the  way,  is  what  is  known  as  "  crude  " 
petroleum,  a  somewhat  misleading  term,  since  it  is  the 
residuum  left  after  the  lighter  oil  used  for  burning  in 
lamps  has  been  distilled.  It  is  therefore  a  waste  pro- 
duct, and  consequently  cheap. 

Reference  was  made  just  now  to  the  "liquor  "  in  the 

284 


The  Manufacture  of  Gas 

hydraulic  mains.  By  this  term  is  meant  water  with 
ammonia  dissolved  in  it,  a  very  plentiful  commodity 
about  a  gas-works,  for  it  is  not  only  found  in  the 
hydraulic  main  but  comes  from  the  washers  and 
scrubbers  in  large  quantities.  In  large  works,  and 
many  small  ones  too,  there  is  a  special  plant  for  recover- 
ing the  ammonia,  which  then  becomes  a  valuable  by- 
product. 

Coal-tar,  the  other  principal  by-product  of  the  gas- 
works (of  course  leaving  out  coke)  is  chemically  one 
of  the  most  wonderful  substances  known  ;  from  it 
are  manufactured  such  various  things  as  dyes,  benzol, 
a  spirit  used  for  driving  motor-cars,  a  substitute  for 
sugar,  and  photographic  chemicals.  The  gas-engineer 
usually  prefers  to  get  rid  of  it  not  by  selling  it  but  by 
turning  it  as  far  as  possible  into  gas,  but  there  is  a  very 
modern  form  of  gas  manufacture  in  which  the  gas  itself 
is  a  by-product,  and  the  large  quantity  of  tar  produced 
is  an  important  feature  of  the  process. 

The  process  referred  to  is  the  manufacture  of  a  fuel 
called  coalite. 

As  we  have  seen,  when  coal  has  been  subjected 
to  a  heat  of  about  2000°  Fahr.  in  a  retort,  certain 
things  in  it  are  dispersed  and  coke  is  left.  This,  we 
all  know  from  our  own  experience,  is  a  smokeless  fuel, 
and  in  that  superior  to  ordinary  coal,  but  it  has  the 
disadvantage  that  it  will  not  ignite  readily,  and  does  not 
burn  with  quite  such  a  cheerful  blaze.  Consequently 
it  is  not  popular  for  domestic  use.  If,  however,  instead 
of  2000°  the  coal  is  only  heated  to  800°,  the  coke 
which  is  produced  is  somewhat  different.  While  it  is 
smokeless,  like  ordinary  "  high-temperature "  coke,  it 
ignites  readily,  and  burns  more  like  coal.  This  i(  low- 
temperature  "  coke  has  been  named  "  coalite,"  and  it  is 
claimed  for  it  that  it  is  going  to  provide  us  with  a 
suitable  fuel  for  use  in  our  houses — easy  to  light , 

285 


The  Manufacture  of  Gas 

cheerful  to  look  at,  giving  more  heat  than  a  coal-fire, 
and  at  the  same  time  abolishing  the  smoke  nuisance. 
The  prospect  of  clear  skies  and  no  fog,  even  in  our 
great  cities,  is  a  very  alluring  one,  and  it  is  hoped  that 
this  new  fuel  will  soon  achieve  all  the  success  that  is 
claimed  for  it. 

From  an  engineering  point  of  view,  however,  the 
chief  interest  lies  in  the  method  of  production  and  also 
in  the  valuable  by-products. 

Instead  of  the  usual  type  of  retort,  special  vertical 
retorts  made  of  iron,  are  used.  Imagine  an  oblong 
cast-iron  box,  with  twelve  holes  in  the  bottom,  each  of 
the  holes  being  the  outlet  from  a  vertical  pipe  fixed 
under  the  box.  There  you  have  a  good  idea  of  the 
"  coalite "  retort.  The  pipes  are  about  9  feet  long, 
4^  inches  in  diameter  at  the  top,  and  slightly  larger  at 
the  bottom.  The  lower  end  is  closed  by  a  door,  so 
that  when  coal  is  tipped  into  the  box  (which  we  may 
really  call  the  "mouthpiece''  of  the  retort)  it  falls  down 
into  the  pipes  and  fills  them  ;  while  to  discharge  them  it 
is  only  necessary  to  open  the  door  at  the  bottom. 
They  are,  of  course,  set  in  brickwork,  and  heated  by 
producer  gas. 

Now  the  remarkable  thing  is  that  the  difference  in 
the  temperature  applied  to  the  coal  brings  about  a  result 
differing  not  only  in  quantity  (as  might  be  expected)  but 
in  kind.  It  would  seem  reasonable  to  suppose  that  the 
lower  temperature  would  produce  tl  underdone,"  and 
therefore  heavier,  coke,  because  less  changed  from  its 
original  state  as  coal,  less  gas,  and  less  tar. 

As  a  matter  of  fact,  a  ton  of  coal  treated  by  the  low- 
temperature  process  gives  roughly  the  same  weight  of 
coalite,  less  gas,  less  ammonia,  but  more  than  twice  as 
much  tar  as  it  does  by  the  high-temperature  process  ; 
tar,  moreover,  which  differs  so  much  from  ordinary 
gas-tar,  that  it  may  be  regarded  almost  as  a  different 

286 


The  Manufacture  of  Gas 

substance.  Treated  chemically,  this  tar  yields  motor- 
spirit,  fuel  oil,  disinfectants,  an  excellent  insulating 
material  for  electric  cables,  besides  other  things.  It  is 
this  valuable  tar  that  makes  the  process  commercially 
possible. 

There  is  one  feature  about  a  gas-works  which  always 
attracts  attention,  on  account  of  its  huge  size.  I  mean 
the  gas-holder. 

It  is  often  spoken  of  as  a  gasometer,  a  term  which 
is  somewhat  misleading,  for  it  suggests  a  measuring 
appliance.  It  is  quite  true  that  the  height  of  a  gas- 
holder tells  the  quantity  of  gas  in  it,  but  it  is  not  used 
for  that  purpose.  It  is  simply  a  huge  flexible  chamber, 
capable  of  expanding  or  contracting  as  the  gas  comes 
in  or  goes  out. 

First  of  all,  a  great  tank  is  built,  generally  under- 
ground, and  frequently  constructed  of  concrete.  Some- 
times, however,  it  is  made  of  iron  plates,  and  then  it 
can  be  placed  above  ground.  This  tank  is  filled  with 
water,  and  its  purpose  is  to  enable  the  holder  to  slide 
up  and  down  freely,  yet  without  the  gas  being  able  to 
escape. 

The  holder  itself  consists  of  a  cylindrical  steel  vessel, 
closed  at  the  top,  but  open  at  the  bottom.  It  is  placed 
in  the  tank,  and  when  empty,  sinks  right  down  into  the 
water.  The  gas  enters  through  a  vertical  pipe  which 
comes  up  through  the  floor  of  the  tank  and  has  an 
open  end  just  above  the  water-level.  The  pressure  of 
the  gas  is  not  very  great,  but  it  is  sufficient,  when 
spread  over  the  large  area  of  the  roof  of  the  holder,  to 
be  able  to  lift  it  up,  and  so  as  the  gas  enters  it  makes 
room  for  itself  by  raising  the  holder  bodily.  Since  the 
latter's  lower  edge  dips  into  the  water,  however,  the 
gas  is  prevented  from  escaping,  whatever  the  position 
of  the  holder  may  be. 

An  outlet   is   provided   for  the   gas  by  means  of  a 

287 


The  Manufacture  of  Gas 

second  vertical  pipe,  and  when  the  gas  is  going  out 
faster  than  it  comes  in,  the  holder,  of  course,  descends 
accordingly. 

Where  the  holder  consists  of  a  single  cylinder,  it  is 
known  as  a  "  one-lift "  gas-holder,  but  in  most  modern 
holders  there  are  two,  three,  or  even  four  cylinders, 
working  one  inside  another,  telescope-fashion.  The 
thought  occurs  at  once — what  keeps  the  gas  from 
escaping  at  the  joints  between  the  cylinders  ?  This  is 
provided  against  by  a  very  ingenious  contrivance. 

Take,  for  example,  the  case  of  a  "  three-lift "  holder. 
The  topmost  section  is  inside  the  others,  and  it  has  all 
around  its  bottom  edge,  on  the  outside,  a  deep  gutter, 
capable  of  holding  water.  On  the  top  edge  of  the  next 
section,  but  inside,  there  is  a  similar  gutter  in  an  inverted 
position,  so  that  the  inverted  gutter  on  the  one  can  hook 
into,  as  it  were,  the  gutter  on  the  other.  Now  it  is  the 
upward  pressure  of  the  gas  upon  the  roof  which  lifts 
the  holder,  and  as  it  is  only  the  inside  one  which 
possesses  a  roof,  it  follows  that  that  must  be  the  first 
one  to  rise.  Before  its  lower  edge  gets  clear  of  the 
water  in  the  tank,  its  gutter,  filled  with  water,  hooks 
under  the  inverted  edge  of  the  next  section,  making  a 
gas-tight  joint  with  it.  The  second  section  in  turn 
does  just  the  same  with  the  third,  which  never  entirely 
leaves  the  tank.  Thus,  no  matter  how  they  may  rise 
and  fall,  there  is  always  a  perfect,  water-sealed  joint  at 
each  point. 


288 


CHAPTER   XXII 
ELECTRIC   LIGHTING   AND   HEATING 

QUITE  primitive  tribes  have  discovered  that,  by  twirling 
a  stick  between  his  hands  while  its  point  touches 
another  piece  of  wood,  a  man  can  kindle  a  fire. 

The  reason  of  this  phenomenon  is  that  there  is 
friction  between  the  stick  and  the  other  piece  of  wood, 
and,  when  spinning  the  stick  round,  the  man  expends 
energy  in  order  to  overcome  the  friction.  It  is  one  of 
Nature's  great  laws  that  no  energy  can  be  lost,  so  the 
energy  of  the  man  cannot  be  lost ;  it  is  simply  con- 
verted from  energy  of  motion  into  heat,  which  is 
manifested  at  the  point  where  the  friction  takes  place. 

Now  it  is  a  very  remarkable  thing,  but  the  principle 
upon  which  we  generate  light  and  heat  by  electricity  is 
exactly  the  same  as  that  which  underlies  the  savage's 
"  fire-stick "  just  described.  An  engine  drives  a 
dynamo,  thereby  forcing  electricity  along  a  wire  ;  we 
put  in  its  path  some  obstacle,  such  as  a  narrow  gap 
across  which  it  has  to  leap,  or  a  fine  wire  through 
which  it  has  to  pass,  by  that  means  producing  some- 
thing analogous  to  mechanical  friction,  and  the  result 
is  that  the  mechanical  energy  of  the  engine  is  converted 
into  heat  at  the  point  where  the  obstacle  is.  Indeed,  it 
is  interesting  to  start  one  step  farther  back  still,  and 
remember  that  the  engine  is  driven  by  heat.  We 
start  with  heat  energy,  which  is  changed  by  the  engine 
into  mechanical  energy,  only  to  be  converted  immedi- 
ately by  the  dynamo  into  electrical  energy,  which 

289  T 


Electric  Lighting  and  Heating 

is  then  turned  back  by  the  lamp  or  heating  appliance 
into  heat  once  more.  Thus  we  have  a  perfect  endless 
series,  the  original  heat,  after  several  changes,  being 
restored  to  what  it  was  to  commence  with. 

The  simplest,  and  at  the  same  time  the  most  familiar 
of  the  appliances  used  for  turning  electricity  into  heat, 
is  the  incandescent  electric  lamp,  or  glow-lamp  as  it  is 
often  called.  The  current  is  led  to  the  lamp  by  a 
comparatively  thick  wire,  which  offers  little  resistance, 
but  in  the  interior  of  the  lamp  itself  it  has  to  pass 
through  a  very  fine  "  filament,"  which  offers  very  great 
resistance  to  its  passage.  Consequently  the  energy 
of  the  electricity  is  absorbed  in  forcing  its  way  through 
the  filament,  and  it  emerges  from  the  other  side  of  the 
lamp  with  scarcely  any  force  left,  the  energy  having 
been  converted  into  heat  in  the  filament,  which  conse- 
quently glows  with  a  bright  light. 

This  heat  would,  if  proper  precautions  were  not 
taken,  cause  the  fine  filament  to  be  burnt  up  almost 
immediately  ;  it  is  therefore  enclosed  in  an  air-tight  glass 
bulb  from  which  practically  all  air  has  been  withdrawn, 
and  since  nothing  can  burn  without  the  presence  of 
oxygen,  the  absence  of  oxygen  in  the  bulb  preserves 
the  delicate  filament  and  permits  it  to  be  heated  without 
being  destroyed. 

The  pumping  out  of  the  air  from  the  bulb  of  an 
electric  lamp  is  a  very  important  matter,  and  no  ordi- 
nary mechanical  air-pump  is  able  to  do  it  well  enough  ; 
air  escapes  through  the  valves,  or  past  the  piston,  and 
so  a  sufficiently  good  vacuum  is  not  produced.  A 
beautifully  simple  little  appliance  is  therefore  used, 
called  a  mercury  air-pump.  It  has  no  valves  ;  the 
cylinder  consists  of  a  glass  tube,  and  drops  of  mercury 
sliding  down  inside  it  form  a  succession  of  pistons. 
The  drops  of  mercury  make  such  perfect  contact  with 
the  sides  of  the  tube  that  no  air  can  possibly  get  past. 

290 


Electric  Lighting  and  Heating 

Originally  the  filaments  were  made  of  carbon.  This 
was  produced  by  mixing  a  paste  of  some  suitable  sub- 
stances, composed  mainly  of  carbon,  forcing  it  through 
a  small  hole  so  as  to  form  a  fine  thread,  and  then  heat- 
ing it  gently  by  an  electric  current  until  all  the  sub- 
stances other  than  carbon  had  been  burnt  out  and  a 
thread  of  practically  pure  carbon  left.  These  "  carbon 
filament"  lamps  are  now  being  largely  superseded  by 
the  more  modern  "  metal  filament "  lamps,  in  which 
the  filament  is  made  of  one  of  several  rare  metals,  such 
as  tungsten  and  tantalum.  These  give  as  much  light 
as  the  older  lamps,  and  consume  less  than  half  as 
much  current.  At  first  there  was  great  difficulty  in 
forming  fine  threads  or  wires  of  these  metals,  and  the 
difficulty  had  to  be  got  over  by  a  process  known  as 
sintering.  The  metal  is  reduced  to  a  powder  and 
mixed  with  a  temporary  cement  into  a  paste,  so  that 
it  can  be  forced  through  a  small  hole,  and  so  formed 
into  a  fine  thread,  much  as  the  carbon  filament  is 
made.  It  is  then  heated  by  an  electric  current,  which 
burns  away  the  cement  and  welds  the  particles  of 
metal  together,  so  that  the  final  result  is  a  fine 
wire  of  pure  metal.  Quite  recently,  however,  a  method 
has  been  discovered  of  drawing  these  metals  into  wire 
directly,  avoiding  the  somewhat  roundabout  process 
just  described. 

The  other  method  of  producing  heat  by  electricity  is 
exemplified  in  the  familiar  (t  arc-lamp."  In  this  there 
are  two  "  pencils  "  of  carbon,  a  material  which  is  found 
deposited  on  the  walls  of  the  retorts  in  gasworks.  As 
the  word  pencil  indicates,  these  pieces  of  carbon  are 
frequently  similar  in  shape  to  a  sharpened  lead-pencil, 
and  they  are  placed  in  the  lamp  with  their  points 
touching.  On  current  being  passed  through,  from 
one  to  the  other,  a  certain  amount  of  heat  is  generated 
at  the  point  where  they  meet,  owing  to  the  fact 

291 


Electric  Lighting  and  Heating 

that  they  do  not  make  a  perfect  contact,  and  the 
electricity  experiences  a  little  difficulty  in  flowing  past 
that  point.  Thus  the  tips  of  the  carbons  become  hot, 
and  a  little  cloud  of  vaporous  carbon  is  formed.  At 
the  same  moment  a  mechanism  which  forms  part  of  the 
lamp,  and  which  is  worked  by  a  magnet  energised  by 
the  current  itself,  draws  the  two  carbons  apart  a  little 
distance.  Although  they  cease  to  touch,  the  carbon 
vapour  forms  a  sufficiently  good  conductor  to  enable 
the  current  to  go  on  flowing  across  the  space,  but 
nevertheless  the  resistance  is  sufficient  to  cause  very 
intense  heat  to  be  generated.  This  raises  the  points 
of  the  carbons  to  a  white  heat  and  so  produces  the 
light.  The  carbons  suffer  a  gradual  consumption  at 
the  points,  and  so  the  distance  between  them  becomes 
increased.  That  increases  the  resistance,  however,  and 
consequently  reduces  the  quantity  of  current  which 
passes  through  the  magnet.  In  this  way  the  strength 
of  the  magnet  is  reduced,  and  the  carbons  then  come 
nearer  together  again,  until  they  are  the  correct  distance 
apart.  Thus  the  lamp  automatically  adjusts  itself,  as 
the  carbons  are  burnt  away. 

There  are  some  special  forms  of  arc-lamp  in  which 
the  carbons  are  impregnated  with  special  materials 
in  order  to  produce  a  redder  and  warmer  light  than 
the  familiar  blue  light  of  the  ordinary  arc-lamp.  These 
are  known  as  "  flame  arcs."  In  others  the  same  result 
is  sought  to  be  achieved  by  enclosing  the  arc  in  a  glass 
globe  containing  certain  gases,  which  glow  and  give  a 
warmer  colour  to  the  light. 

For  purely  heating  purposes,  very  similar  methods 
are  employed.  For  domestic  use  there  are  many 
appliances  such  as  radiators,  water-heaters,  cooking 
stoves,  foot-warmers,  even  warm  bandages  and  heated 
carpets,  constructed  upon  the  same  principle  as  the 
glow-lamp.  There  are  coils  of  wire,  of  platinum,  or  of 

292 


Electric  Lighting  and  Heating 

some  alloy  which  will  stand  being  heated  in  contact 
with  air  (for  it  is  obvious  that,  when  required  to  give 
out  its  heat,  the  wire  must  not  be  enclosed  in  a  vacuum), 
and  these  coils  are  heated  by  means  of  a  current  of 
electricity.  These  appliances  have  the  great  advantage 
in  a  house  that  they  consume  no  air,  and  in  most  of 
them  there  are  a  number  of  separate  coils,  so  that,  by 
sending  the  current  through  fewer  or  more  of  them, 
the  heat  can  be  nicely  regulated. 

Small  furnaces  for  chemical  experiments,  or  for 
dentists'  work,  coffee-roasters,  and  many  other  heating 
appliances  besides  those  for  domestic  use,  are  made 
in  this  way.  The  system  is  only  suitable,  however, 
where  moderate  temperatures  are  required.  For  high 
temperatures  the  principle  of  the  arc-lamp  is  generally 
followed,  though  not  invariably. 

The  heat  produced  in  that  little  space  between  the 
two  carbon  pencils,  known  as  the  "  arc,"  is  almost  in- 
conceivable. It  is  estimated  that  in  a  lamp  the  positive 
pencil — that  is,  the  one  to  which  the  current  is  led — 
exceeds  6000°  F.  All  metals,  even  platinum,  will 
quickly  melt  if  exposed  to  it,  and  thus  the  "  electric 
arc"  enables  us  to  construct  the  most  powerful  fur- 
naces known.  This  seems  at  first  sight  strange  ;  for, 
since  the  heat  given  by  electricity  is  only  a  repro- 
duction of  the  heat  of  a  coal  fire,  it  appears  as  if  the 
former  could  not  by  any  possible  means  exceed  the 
latter.  The  explanation  is  that  electricity  provides  us 
with  a  method  by  which  we  can  concentrate  the  heat 
of  a  large  body  of  coal  in  a  very  small  space. 

Iron  is  now  being  smelted  in  electric  blast  furnaces,1 
and  electric  furnaces  for  making  steel  have  been  in 
operation  for  some  years.  Two  such  are  shown  in 
Figs.  40,  41,  and  42.  Many  manufacturing  processes 

1  It  appears  probable  that  the  electric  furnace  will  provide   a  means  of 
making  steel  direct  from  iron  ore. 

293 


Electric  Lighting  and  Heating 

which  not  long  ago  were  impracticable,  through  lack 
of  a  means  of  producing  a  sufficiently  intense  heat,  are 
now  carried  on  by  electric  furnaces.  Most  of  these 
are  on  the  principle  of  the  (t  arc/'  the  substance  to  be 
melted  being  placed  in  or  near  the  gap  across  which 
electricity  is  passing.  These  furnaces  are  of  special 
value  in  some  places  where  there  is  little  fuel  to  be 


=  Molten  Mehl    —--*  — 


Iron  Plug 


Cables  tedding  to  the  Dynamo. 


FIG.  40.— The  "Girod"  Electric  Steel  Furnace  ("arc  type).  The  furnace 
consists  of  a  steel  vessel  lined  with  a  heat-resisting  lining.  Over  the 
centre  there  are  suspended  one  or  more  blocks  of  carbon,  while  in  the 
floor  of  the  furnace  are  a  number  of  iron  plugs.  At  first  the  carbon 
blocks  are  lowered  into  contact  with  the  metal  in  the  furnace,  and  the 
current,  being  switched  on,  flows  from  them  through  the  metal  to  the 
iron  plugs.  Then  the  carbon  block  is  raised,  and  a  powerful  arc  is  formed 
between  it  and  the  surface  of  the  metal. 

had,  but  plenty  of  water-power.  Current  for  the  fur- 
nace can  then  be  generated  by  the  water-power,  and 
the  lack  of  fuel  is  of  no  moment.  It  is  interesting  to 
note  that  even  then  heat  is  the  original  source  of  the 
power,  for  it  is  the  sun's  heat  which  makes  the  rain 
which  gives  the  water-power. 

In  the  welding  of  metals  the  electric  arc  can  accom- 
plish wonders.  Suppose  two  bars  of  iron  need  to  be 
welded  together.  One  plan  is  to  put  them  on  insulators, 

294 


Electric  Lighting  and  Heating 

with  their  ends  touching,  and  to  send  a  current  through 
from  one  bar   to  the  other.     Owing  to  their  making 


FIG. 
41. 


As  seen 
from 
above. 


FIG.    £ 
42. 


As  seen 
/     through 
centre. 


Another  kind  of  Electric  Steel  Furnace  (induction  type).  F.  F.  F.— the 
furnace  proper,  formed  like  a  circular  trough.  M.  M.  M. — the  molten 
metal  in  the  trough.  C.  C.  C. — a  coil  of  wire  round  the  furnace.  In 
this  kind  of  furnace  the  heat  is  produced  by  current  flowing  through  the 
metal  itself,  just  as  it  is  in  an  incandescent  lamp  by  current  flowing 
through  the  filament.  The  current  is  not  led  to  the  iron  from  a  dynamo, 
but  is  actually  generated  in  it  by  induction.  The  furnace  takes  the  form 
of  a  circular  trough,  outside  which  is  a  coil  of  wire.  Thus  it  is  practically 
a  huge  induction  coil,  and  powerful  alternating  currents  in  the  outer  coil 
induce  currents  in  the  ring  of  molten  metal  lying  in  the  trough. 

an   imperfect   contact,  heat   is   generated   at  the  point 
where  they  touch.      Thus  they  are  soon  brought  up  to 

295 


Electric  Lighting  and  Heating 

welding  heat,  and,  on  being  pressed  together,  become 
united.  Very  large  bars  can  be  welded  in  this  way, 
and  bars  of  awkward  shapes  which  it  would  be  im- 
possible to  weld  in  the  ordinary  way  by  heating  in 
a  fire. 

Whenever  great  heat  needs  to  be  applied  locally  to 
some  part  of  a  piece  of  metal,  whether  for  welding  or 
any  other  purpose,  the  arc  forms  a  very  convenient 
means  of  doing  it.  The  usual  method  is  to  lead  the 
current  to  the  metal  to  be  treated.  The  workman  is 
provided  with  a  carbon-rod  fixed  in  an  insulating 
handle,  to  which  is  attached  a  shield  to  protect  his 
hand  from  the  heat.  The  carbon  rod  is  connected  to 
the  return  wire,  so  that  as  soon  as  it  is  placed  upon 
the  metal,  current  commences  to  pass,  after  which 
the  rod  is  withdrawn  a  little  distance  and  the  condi- 
tions which  obtain  in  an  arc-lamp  are  set  up  almost 
exactly.  In  the  case  of  the  lamp,  as  we  have  seen,  the 
positive  carbon  is  raised  to  a  very  intense  heat,  and 
as,  in  the  arrangement  just  described,  the  metal  itself 
occupies  the  place  of  the  positive  carbon  in  the  lamp, 
it  follows  that  it,  too,  will  likewise  be  raised  to  an 
intense  heat.  Thus,  if  an  iron  or  steel  casting,  for 
example,  be  found  to  contain  a  fault,  the  metal  may  by 
this  means  be  remelted  at  that  particular  point  and 
the  fault  practically  removed. 

It  will  probably  be  assumed  that  to  produce  this 
great  heat  needs  current  at  very  high  pressure,  and  that 
therefore  it  is  dangerous  work.  On  the  contrary,  while 
a  very  large  volume  of  current  is  used,  running  often 
into  thousands  of  amperes,  the  pressure  is  quite 
moderate,  not  more  than  forty  or  fifty  volts,  quite  in- 
sufficient under  ordinary  circumstances  to  cause  a 
man  any  serious  injury. 

The  subject  of  lighting  and  heating  being  largely  a 
domestic  matter,  naturally  leads  us  to  think  of  the 

296 


Electric  Lighting  and  Heating 

public  mains  by  which  the  current  is  brought  along  the 
streets  to  our  own  doors.  These  are  invariably  of 
copper,  generally  encased  in  an  insulating  covering  of 
indiarubber  and  tape,  placed  in  pipes  buried  under  the 
pavements.  The  pipes  are  first  laid  like  any  other 
pipes,  and  then  the  cable  is  drawn  through  by  main  force. 
At  frequent  intervals  there  are  cast-iron  boxes,  called 
"  junction  boxes,"  where  the  branch-wires  join  on  to  the 
main  cables. 

There  are  instances  in  which,  instead  of  insulated 
cables,  bare  copper  strips  are  used,  stretched  upon  in- 
sulators in  pipes.  This  idea,  however,  does  not  find 
general  favour. 

In  distributing  current  from  a  generating  station 
by  means  of  a  network  of  cables  and  wires,  the  elec- 
trical engineer  is  faced  with  many  difficulties.  The 
chief  of  these  is  to  keep  the  pressure  from  varying 
at  different  points  in  the  system  under  varying  con- 
ditions. 

Copper  is  a  good  conductor,  but  it  is  not  perfect.  It 
offers  some  resistance,  and  consequently  takes  out  from 
the  current  some  of  its  energy,  which  it  converts, 
according  to  the  principle  we  have  just  been  discussing, 
into  heat.  The  effect  of  this  is  that,  at  the  farther  end  of 
a  long  cable  the  pressure  will  be  considerably  less  than 
that  generated  by  the  dynamo.  If  the  current  is  only 
taken  for  use  from  the  far  end  of  the  cable  that  does  not 
matter,  for  it  can  be  generated  at  a  higher  voltage  in  the 
dynamo,  so  that  by  the  time  it  reaches  the  other  end  it 
is  just  correct.  But  supposing  there  are  lamps  con- 
nected to  the  cable  at  frequent  intervals  all  along  its 
length  ;  if  a  number  of  these  are  switched  on,  near  the 
dynamo,  the  pressure  at  the  farther  end  will  be  reduced 
more  than  it  is  when  only  those  at  the  other  end  are 
alight.  So,  according  to  the  varying  number  of  lamps 
alight  over  the  system,  the  relative  pressure  at  the  dif- 

297 


Electric  Lighting  and  Heating 

ferent  points  will  be  constantly  changing.  This  accounts 
for  the  varying  degrees  of  brightness  in  the  lights,  which 
we  have  all  noticed  at  times. 

This  difficulty  cannot  be  entirely  overcome.  It  can 
be  mitigated,  however,  by  using  cables  of  ample  size,  so 
that  there  may  be  a  free  flow  of  current,  as  it  were, 
even  when  the  demand  is  greatest,  and  by  care  and 
watchfulness  at  the  generating  station. 

At  every  public  generating  station  there  are  storage- 
batteries  or  accumulators.  These  are  charged  by  the 
dynamos  when  the  demand  for  current  outside  is  not 
heavy,  and  they  form  a  reserve  which  can  be  drawn 
upon  in  case  of  need.  If,  for  example,  a  sudden  dark- 
ness causes  a  lot  of  lamps  to  be  switched  on  at  once  the 
demand  for  current  may  be  so  great  that  the  dynamo 
cannot  keep  the  pressure  up.  Then  the  switchboard 
attendant  can  switch  in  some  of  the  cells  of  the  storage 
battery  to  assist  the  dynamo.  Moreover,  if  an  accident 
should  cause  a  momentary  stoppage  of  the  machinery, 
the  storage  battery  can  keep  the  lights  going  for  a  short 
time  by  itself. 

The  cost  of  the  copper  in  the  distributing  cables  is  a 
very  serious  item  in  an  electric-light  installation,  and 
has  led  to  the  invention  of  a  very  interesting  arrange- 
ment known  as  "  the  three-wire  system,"  in  which  two 
thick  wires  and  a  thin  one  are  made  to  do  the  work  of 
four  thick  wires. 

To  understand  this  we  must  refer  to  the  two  dia- 
grams, Figs.  43  and  44.  The  two  large  circles  represent 
dynamos,  the  small  circles  lamps,  and  the  horizontal 
lines  wires.  We  will  assume  that  the  current  supplied 
to  consumers  is  at  1 10  volts,  and  consequently  the 
lamps  in  use  are  constructed  for  that  voltage. 

In  the  former  diagram  each  dynamo  has  its  own  two 
wires  through  which  it  supplies  current  to  a  lamp.  The 
lamp  needs,  say,  one  ampere,  so  that  each  dynamo  has  to 

298 


Electric  Lighting  and  Heating 

generate  one  ampere  at  no  volts,  and  each  of  the  four 
wires  needs  to  be  large  enough  to  carry  one  ampere. 
Now  turn  to  the  second  diagram.     There  the  two 


FIG.  43. 


FIG.  44. 

Diagrams  showing  how  three  wires  are  made  to  do  the  work  of  four. 

dynamos  are  joined  together  "  in  series/'  that  is,  one 
behind  the  other,  and  when  two  dynamos  are  joined 
together  in  that  manner  they  together  generate  the 

299 


Electric  Lighting  and  Heating 

same  quantity  of  current  that  either  of  them  would  do 
by  itself,  but  at  twice  the  pressure.  Therefore  these  two 
will  generate  current  at  220  volts  instead  of  no.  In 
a  similar  way  if  two  lamps,  each  of  which  needs  no 
volts,  be  coupled  together  "in  series"  so  that  the  same 
current  passes  through  both,  they  will  only  use  the 
same  quantity  of  current  that  either  would  do  by  itself, 
but  it  will  need  to  be  at  twice  the  voltage. 

Suppose  then  we  rearrange  our  lamps  as  at  i  and  2 
(Fig.  44),  the  current  will  pass  along  the  top  wire 
through  lamp  i,  then  through  lamp  2,  and  back  along 
the  bottom  wire.  The  two  lamps  will  therefore  be  "  in 
series,"  and  will  require  current  at  220  volts,  exactly 
what  the  two  dynamos  "  in  series  "  are  prepared  to 
supply  ;  and  they  will  only  need  one  ampere  for  the  two, 
whereas  in  the  former  figure,  with  the  two  dynamos 
working  separately,  they  needed  one  ampere  each. 

Thus,  in  the  first  arrangement  we  need  four  wires, 
each  capable  of  carrying  one  ampere,  while  in  the 
second  we  light  our  lamps  just  the  same,  but  only  need 
two  wires,  capable  of  carrying  one  ampere  each — a 
clear  gain  of  the  cost  of  two  wires. 

Of  course,  I  have  assumed,  for  simplicity's  sake,  a 
case  in  which  two  dynamos  are  employed  to  light  two 
lamps  only,  a  state  of  affairs  which  would  not  exist  in 
practice,  but  which  serves  the  purpose  of  illustration, 
for  the  principle  which  applies  to  two  lamps  applies 
equally  well  to  two  thousand,  or  any  other  number. 

We  have  not  yet,  however,  seen  the  purpose  of  the 
third  (middle)  wire.  In  order  to  see  this,  we  must 
imagine  some  more  lamps,  joined  up  as  at  3,  4,  5,  and 
6.  If  these  are  all  switched  on  at  once  the  condition 
of  things  is  exactly  the  same  as  it  is  for  i  and  2  only, 
for  current  will  pass  along  the  top  wire ;  one  ampere 
will  go  through  the  lamps  3  and  4,  and  another  through 
5  and  6,  exactly  as  the  one  ampere  went  through  i 

300 


Electric  Lighting  and  Heating 

and  then  through  2.  Thus,  so  long  as  the  two  sets 
of  lamps — those  connected  between  the  upper  and  middle 
wires,  and  those  between  the  middle  and  lower — are 
taking  an  equal  quantity  of  current,  everything  is  ex- 
actly the  same  as  in  the  simple  example  of  the  two 
lamps. 

But  suppose  we  switch  one  lamp  out,  say  No.  4. 
The  one  ampere  which  passes  through  No.  3  will  then 
be  blocked,  and  will  return  through  the  middle  wire  to 
the  dynamos.  But  the  middle  wire  is  not  connected  to 
the  two  dynamos  "  in  series,"  but  to  the  joint  between 
them  ;  therefore  the  current  which  goes  through  3  and 
returns  by  the  middle  wire,  will  be  generated  by  dynamo 
A  only,  and  will  be  only  no  volts,  the  correct  pressure 
for  a  single  lamp.  On  the  other  hand  if,  instead  of  4, 
one  of  the  upper  set  be  switched  out,  say  5,  the  current 
for  No.  6  will  be  generated  by  dynamo  B,  and  will  flow 
along  the  middle  wire  and  back  by  the  lowest  one. 
Thus,  the  duty  of  the  middle  wire  is  to  carry  to  or 
from  the  dynamo  (as  the  case  may  be),  the  difference 
in  current,  the  amount  by  which  the  current  consumed 
by  one  set  of  lamps  exceeds  that  consumed  by  the 
other  set,  and  as  the  lamps  are  always  arranged  so 
that  this  difference  cannot  be  very  much,  the  middle 
wire  may  be  quite  small. 

Thus,  we  see,  the  work  of  four  large  wires  can  be 
done  by  two  wires  of  the  same  size,  and  one  very  thin 
one,  representing  a  considerable  saving  in  a  large  in- 
stallation. 

In  conclusion,  reference  may  be  made  to  a  machine 
which  may  be  noticed  in  many  generating  stations,  and 
which  is  somewhat  mystifying  to  a  visitor.  It  is  called 
a  motor  generator,  and  looks  like  two  dynamos,  or  even 
three,  placed  side  by  side  on  the  same  base,  apparently 
working  each  other. 

Its  purpose  is  this.  There  may  be  an  outlying 

301 


Electric  Lighting  and  Heating 

district  supplied  from  that  station,  and,  because  of  the 
resistance  of  the  long  cable,  the  current  needs  to  be 
sent  out  at  a  higher  voltage  than  that  sent  to  the 
nearer  districts.  It  is  not  worth  while  to  have  a 
special  engine  and  dynamo  to  supply  this  one  cable, 
so  current  from  the  other  dynamos  is  taken  and  made 
to  drive  a  motor,  which  turns  a  small  dynamo  so 
wound  with  wire  that  it  generates  the  voltage  required. 
Where  the  three-wire  system  is  in  use,  the  motor  has 
to  drive  two  small  dynamos,  and  that  accounts  for  there 
sometimes  being  three  machines  together. 


302 


CHAPTER   XXIII 

MEASURING   TO   A   HAIR'S   BREADTH 

THERE  is  in  existence  a  letter  written  by  James  Watt, 
in  which  he  mentions,  as  a  reason  for  gratification,  that 
at  his  works  at  Birmingham  they  had  just  bored  a 
steam-engine  cylinder  so  accurately  that  it  was  not 
more  than  three-eighths  of  an  inch  out  of  a  true  circle. 
That  gives  us  a  measure  of  the  degree  of  accuracy 
attained  at  that  period,  and  it  seems  quite  amusing 
at  the  present  day,  when  it  is  quite  an  ordinary  thing 
to  work  to  one-thousandth  of  an  inch. 

The  difference  is  due  mainly  to  the  vast  improve- 
ments in  the  construction  of  the  lathes  and  other 
machine-tools  with  which  the  work  is  done.  This 
improvement  also  makes  possible  a  degree  of  standardisa- 
tion which  is  very  important,  but  which  was  out  of  the 
question  in  the  old  days.  Take,  for  example,  a  machine 
such  as  a  steam-pump,  of  which  there  are  many  sent 
to  the  most  out-of-the-way  parts  of  the  earth.  It  used 
to  be  the  plan  to  "  fit "  each  one  up  in  the  workshop, 
each  piece  being  made  to  fit  the  parts  with  which  it 
was  connected.  The  cylinder  would  be  bored,  for 
instance,  and  then  the  piston  turned  to  fit  it,  the  latter 
being  tried  in  the  former  to  see  that  it  was  all  right, 
and  the  same  with  the  other  parts.  The  workman 
made  the  parts  to  fit  each  other  as  he  went  on,  and 
very  beautiful  work  was  done  in  this  way,  but  there 
was  one  great  drawback.  Suppose  one  small  but 
important  part  broke ;  the  machine  might  be  at  a  mine 

303 


Measuring  to  a  Hair's  Breadth 

in  remote  Siberia,  or  the  East  Indies,  but  wherever  it 
might  be,  the  whole  thing  would  probably  have  to  go 
back  to  the  makers  to  have  that  one  part  replaced. 

Where  a  single  machine  is  built,  for  some  special 
purpose,  the  same  old  process  necessarily  obtains  to  a 
great  extent;  but,  where  the  machine  is  made  in  numbers, 
it  is  nowadays  almost  always  standardised.  Each  part 
is  made  "  to  gauge,"  and  has  a  distinguishing  number 
or  code-word,  so  that  a  part  to  replace  one  broken 
can  be  ordered  by  telegraph  and  despatched  immedi- 
ately. This  system  also  tends  to  reduce  the  cost  of 
production,  for  special  labour-saving  devices  can  often 
be  invented  for  producing  the  same  thing  over  and 
over  again ;  and,  moreover,  the  men  get  more  expert 
and  quick  when  employed  constantly  on  producing  the 
same  little  part  than  they  can  possibly  do  if  they  have 
to  make  all  the  parts  in  turn.  There  is,  of  course,  a 
disadvantage  to  be  set  against  this.  A  workman,  who 
sees  a  complete  machine  growing  under  his  hand, 
naturally  feels  a  greater  interest  in  his  work,  and  takes 
a  greater  pride  in  it,  than  one  who  simply  turns  out 
one  particular  part  by  the  thousand. 

Under  these  modern  conditions,  the  putting  together 
of  the  complete  machine,  which  used  to  be  called 
"fitting,"  is  now  more  appropriately  called  "assem- 
bling," for  the  different  parts  come  into  the  "  erecting 
shop  "  all  exactly  alike  and  ready  to  put  together,  and 
very  little  fitting  is  required. 

Now  it  is  obvious  that  this  system  is  only  made 
possible  by  the  use  of  very  accurate  measuring  appli- 
ances. A  workman  used  to  have  a  steel  rule  and  a 
pair  of  callipers,  and  that  was  about  all  ;  if  he  had  to 
turn  a  rod  2  inches  in  diameter,  he  would  set  his 
callipers  at  2  inches  by  his  rule,  and  then  proceed  to 
turn  the  bar  in  the  lathe,  gradually  reducing  its  size, 
and  trying  it  frequently  with  his  callipers  until  he 

304 


Measuring  to  a  Hair's  Breadth 

found  that  they  would  just  pass  over  it.  In  a  modern 
lathe,  however,  intended  for  standardised  work,  he  sets 
the  tool  which  does  the  cutting  in  a  certain  way,  and 
then,  by  turning  a  wheel,  brings  its  edge  up  to  the  bar 
to  be  turned,  and  when  it  has  advanced  far  enough  a 
stop  prevents  it  from  going  any  farther.  Thus  the 
machine  can  be  said  to  do  the  measuring  itself ;  there 
is  no  need  to  use  callipers,  and,  so  long  as  the  adjust- 
ment of  the  machine  is  not  altered,  it  will  go  on  turning 
bars  exactly  2  inches  in  diameter. 

Many  machine-tools  have  "  micrometers "  attached 
to  them,  whereby  their  adjustments  can  be  controlled 
with  great  accuracy.  This  instrument,  as  its  name 
implies,  is  intended  for  measuring  very  minute  distances. 
It  consists  of  a  very  carefully  made  screw,  turning  in  a 
suitable  nut.  Suppose  that  it  has  twenty-five  threads  to 
an  inch  ;  then  if  you  turn  it  round  twenty-five  times,  its 
point  will  advance  or  recede  an  inch  ;  or  if  you  turn  it 
once,  the  movement  will  be  one  twenty-fifth  of  an  inch. 
And  suppose,  further,  that  it  is  fitted  with  a  large  disc-like 
head,  on  the  edge  of  which  are  marks  dividing  it  into 
equal  parts,  say,  for  example,  forty  parts.  We  can 
then  easily  turn  it  exactly  one-fortieth  of  a  revolution, 
and  it  is  quite  clear  that  that  will  move  the  point  of 
the  screw  one-thousandth  of  an  inch.  The  micrometer 
takes  many  forms,  but  that  is  the  principle  of  them  all. 

The  accuracy  of  standard  work  is  always  tested  by 
"  gauges,"  usually  called  "  limit  gauges,"  the  term  limit 
implying  that  they  reach  the  limit  of  accuracy.  In  the 
case  referred  to  just  now,  of  rods  2  inches  in  diameter, 
the  gauge  would  consist  of  a  little  block  of  steel  with  a 
hole  exactly  2  inches  in  diameter  in  it,  and  the  rods 
would  be  tried  by  inserting  them  in  that  hole,  which 
they  should  exactly  fill.  On  the  other  hand,  suppose 
we  were  dealing  with  small  cylinders  which  had  to  be 
bored  out  to  3  inches  diameter  ;  then  the  gauge  would 

305  U 


Measuring  to  a  Hair's   Breadth 

be  a  steel  plug,  of  exactly  the  right  size,  which  would  be 
inserted  in  them. 

But  it  may  be  asked  :  Why,  if  the  tools  are  so  accu- 
rate, are  these  gauges  necessary  ?  The  reason  is  that 
there  may  be  faults  even  in  the  most  perfect  machine  ; 
the  adjustment  may  be  a  little  out,  or  some  part  a  little 
worn  ;  an  instance  of  those  difficulties,  referred  to  in 
the  opening  chapter,  which  crop  up  in  practical  work- 
ing, and  which  the  pure  theorist  is  apt  to  overlook. 

Another  form  of  tool,  which  is  really  a  measuring 
device,  is  known  as  a  "  jig."  These  are  made  in 
innumerable  forms,  each  one  being  specially  devised  for 
a  particular  job,  but  the  idea  underlying  them  can  be 
made  clear  by  a  single  example  which  came  under  my 
notice  recently. 

All  readers  will  be  familiar  with  what  is  called  the 
"  gear  case "  of  a  lawn-mower.  It  is  the  iron  cover 
which  encloses  the  tooth-wheels  on  one  side  of  the 
machine.  It  is  to  start  with  a  plain  iron  casting,  just 
as  it  comes  from  the  iron-foundry,  and  therefore  it 
possesses  certain  irregularities  common  to  all  castings ; 
yet  it  has  to  be  fitted  accurately  to  the  side  of  the 
machine,  for  which  purpose  it  must  have  holes  which 
exactly  coincide  with  corresponding  holes  in  the  other 
part,  and  it  also  has  certain  holes  for  supporting  the 
ends  of  the  axles  on  which  the  tooth-wheels  turn,  and 
these,  too,  must  occupy  the  exactly  proper  positions 
relative  to  the  other  holes.  The  way  it  would  be  done, 
if  a  single  machine  were  being  made,  would  be  to  fix 
the  position  of  one  hole  and  then  measure  those  of  the 
others  from  it.  The  place  for  each  hole  would  first 
be  rubbed  over  with  chalk,  and  the  hole  itself  scratched 
on  the  white  background,  and  finally  the  exact  centre  of 
the  hole  would  be  marked  by  hammering  a  little  sharp- 
pointed  punch  into  it  and  so  making  a  little  dent  in  the 
iron.  Then  the  casting  would  be  taken  to  the  drilling 

306 


Measuring  to  a  Hair's  Breadth 

machine  and  the  holes  drilled  as  nearly  in  the  correct 
position  as  possible,  the  whole  being  a  very  laborious 
and  therefore  costly  proceeding. 

In  the  works  referred  to,  they  have  a  specially  made 
iron  box,  into  which  the  casting  is  placed  and  clipped 
in  position  with  screws.  Then  a  lid  is  placed  on  the 
box  and  fastened  down.  Now  every  hole  that  has  to 
be  drilled  in  the  casting  is  represented  by  a  hole  in  the 
box  or  lid,  so  that  all  that  has  to  be  done  is  to  take  the 
box  to  the  drilling  machine,  and  let  the  drill  pass 
through  each  of  these  holes  into  the  casting  beneath. 
Thus  all  measuring  and  marking  is  saved,  and  the  holes 
are  all  drilled  in  exactly  the  right  places.  The  saving 
in  time  is  obvious,  the  result  is  more  accurate,  and  a 
less  skilled  man  can  do  the  work  ;  moreover,  since  the 
same  box  and  lid  can  be  used  again  and  again,  each  of 
the  covers  is  bound  to  be,  as  far  as  its  holes  are  con- 
cerned, exactly  like  the  others.  The  box  and  lid  form 
a -jig." 

One  of  the  most  marvellous  measuring  appliances  in 
the  world  has  recently  been  invented  and  made  for  the 
Standards  Department  of  the  British  Government.  It 
is  called  a  "  comparator,"  since  its  duty  is  to  compare 
yard  measures  with  the  "  standard  yard  "  and  determine 
the  difference,  if  any. 

The  imperial  standard  yard,  which  is  the  legal  basis 
for  all  measures  of  length  within  the  British  Empire,  is 
a  bar  of  metal  i  inch  square  and  38  inches  long,  the 
metal  being  an  alloy  of  copper,  tin,  and  zinc.  One  inch 
from  each  end  there  is  a  circular  recess,  half-an-inch  in 
diameter  and  half-an-inch  deep,  in  the  centre  of  the 
bottom  of  which  is  fixed  a  little  gold  plug.  On  the 
plug  are  engraved  five  fine  lines — three  vertical  and  two 
horizontal ;  and  the  distance  from  the  centre  one  of 
the  vertical  lines  at  one  end  to  the  corresponding  line 
at  the  other  end,  at  the  temperature  of  62°  F.,  is  one 

307 


Measuring  to  a  Hair's  Breadth 

yard.  This  is  within  one  two-hundredth  of  an  inch  of 
the  standard  yard  of  Henry  VII.,  still  preserved  at  the 
Standards  Office. 

The  whole  apparatus  is  most  complicated  ;  but,  put 
briefly,  this  is  how  it  works.  There  is  a  sliding  table, 
on  which  the  standard  yard  is  placed.  Over  each  end 
of  this  there  is  a  microscope,  so  mounted  that  it  can  be 
moved  by  a  very  fine  screw  adjustment  until  the  line 
on  the  standard  bar  comes  exactly  between  two  threads 
of  spider's  web  stretched  across  the  lens.  When  both 
microscopes  are  thus  adjusted,  the  standard  is  taken 
away,  and  the  bar  which  is  to  be  compared  with  it  is 
put  in  its  place.  The  table  upon  which  it  rests  is  then 
moved  by  a  screw  until  the  mark  at  one  end  of  the  bar 
is  exactly  under  the  microscope  at  that  end.  Then  the 
other  end  mark  is  examined  through  the  other  micro- 
scope, and,  if  it  comes  between  the  spider  lines,  it  is 
correct ;  but,  if  not,  then  the  microscope  is  moved  until 
it  does  so.  The  distance,  then,  that  the  microscope  has 
to  be  moved  is  clearly  the  difference  between  the 
standard  and  the  bar  being  checked. 

A  machine  on  these  lines,  in  which  the  travel  of  the 
microscope  is  measured  by  a  micrometer,  is  in  no  sense 
new  ;  but  in  this  case,  instead  of  the  turns  of  the  micro- 
meter screw,  a  wonderful  natural  scale,  formed  by  the 
decomposition  of  a  beam  of  light,  is  used.  The  divisions 
in  this  marvellous  scale  are  about  ^thnr  (one  forty- 
thousandth)  of  an  inch  apart — I  put  the  fraction  in 
words  lest  readers  should  think  the  printer  had  added 
a  nought  in  error. 

A  beam  of  light,  usually  from  glowing  hydrogen,  is 
first  passed  through  a  prism,  in  order  to  disperse  some 
of  the  rays  and  bring  into  use  just  those  selected  for 
the  purpose.  The  beam  of  this  selected  light  is  then 
allowed  to  fall  upon  and  be  reflected  by  two  pieces  of 
glass.  The  explanation  of  what  happens  belongs  to  a 

308 


Measuring  to  a   Hair's   Breadth 

work  on  light,  and  it  must  suffice  to  say  here  that  the 
result  of  this  reflection  is  to  produce,  in  the  field  of 
view  of  a  small  telescope  fixed  near  by,  a  brightly 
illuminated  background  crossed  by  vertical  dark 
lines. 

Now,  one  of  the  pieces  of  glass  by  which  the  light  is 
reflected  is  fixed  to  the  microscope,  and,  as  it  moves, 
these  dark  lines  pass  like  a  panorama  across  the  field 
of  view  of  the  telescope.  There  are  two  spider  lines 
across  the  lens  of  the  telescope,  and  with  their  aid  it  is 
quite  easy  to  count  the  number  of  lines  that  pass  ;  and 
it  follows  from  the  laws  of  light,  and  the  way  the 
instrument  is  arranged,  that  half  the  number  seen  to 
pass  the  centre  of  the  telescope,  multiplied  by  the  wave- 
length of  the  light  used,  will  give  the  movement  of  the 
microscope.  By  this  means  the  minute  fraction  of  an 
inch  mentioned  just  now  can  be  measured  easily,  and, 
as  the  distance  apart  of  these  dark  lines  depends 
absolutely  upon  the  "  wave-length "  of  the  light,  the 
wave-length  of  light  becomes  a  standard  of  length 
which  may  be  of  great  value  in  years  to  come. 

There  is  a  man,  only  one  man  in  the  world  apparently, 
who  can  rule  fine  clean  straight  lines,  with  a  sharp 
diamond,  a  forty-thousandth  of  an  inch  apart — the 
mark  on  the  British  Standard  Bar,  although  fine  to  the 
naked  eye,  covers  forty-five  of  these  lines — and  it  is 
thought  that  by  using  a  measure  ruled  with  these  fine 
lines,  in  conjunction  with  this  machine,  the  length  of 
the  yard  and  the  metre  can  be  measured  and  expressed 
in  terms  of  the  wave-length  of  light ;  so  that  if,  for  any 
unsuspected  reason,  there  should  be  any  slow  shrinking 
or  expansion  taking  place  in  the  standard  bars  in 
London,  New  York,  and  the  other  capitals,  this  may 
furnish,  as  time  goes  on,  a  means  of  discovering  it. 

The  part  of  the  comparator  where  the  dark  lines  are 
formed  is  called  an  "  interferometer,"  and  the  lines 

309 


Measuring  to  a  Hair's  Breadth 

themselves  "  interference  lines/'  since  they  are  caused 
by  the  waves  of  light  interfering  with  each  other. 

From  the  above  rather  theoretical  piece  of  apparatus 
(for  one  cannot  avoid  the  reflection  that,  for  most 
purposes,  the  fact  that  a  measure  may  be  a  few  forty- 
thousandths  of  an  inch  out  is  of  no  practical  moment 
whatever)  we  can  turn  to  one  of  great  practical  utility, 
a  sounding-machine  by  which,  as  it  goes  along,  a  ship 
may  "  feel "  the  bottom  of  the  sea  and  so  avoid  danger- 
ous shallows.  A  form  of  this  apparatus  commonly 
used,  known  as  "  Wigzell's,"  after  its  inventor,  takes 
advantage  of  the  fact  that  the  pressure  of  the  water  of 
the  sea  depends  upon  the  depth.  At  the  surface  it  is 
nothing,  but  as  one  descends  it  becomes  greater  and 
greater  owing  to  the  weight  of  the  mass  of  water  lying 
above.  This  machine,  then,  is  a  little  cylinder  with  a 
piston  in  it,  the  latter  being  held  back  by  a  silver  spring. 
When  it  is  lowered  into  the  water,  the  pressure  forces 
the  piston  in  against  the  pull  of  the  spring,  and  the 
distance  it  moves  depends  entirely  on  the  amount  of 
the  pressure,  and  therefore  on  the  depth.  The  full 
extent  that  the  piston  moves  is  recorded  by  a  little 
sliding  indicator  which  it  pushes  along,  but  leaves 
behind  when  it  returns  to  its  normal  state,  as  it  is 
drawn  to  the  surface.  From  this  the  depth  is  read, 
and  the  indicator  can  then  be  pushed  back  to 
"  zero/'  when  the  instrument  is  at  once  ready  for  use 
again. 

A  somewhat  similar  device,  invented  by  the  famous 
Lord  Kelvin,  consists  of  a  tube  of  glass,  coated  inside 
with  a  chemical  which  changes  colour  if  brought  into 
contact  with  sea-water.  This  is  lowered  into  the  sea, 
and  the  air  in  the  tube  becomes  compressed,  according 
to  the  pressure  of  water.  The  distance  that  the  water 
penetrates  up  the  tube,  therefore,  represents  the  depth, 

310 


Measuring  to  a  Hair's  Breadth 

and  this  is  recorded  by  the  discolouration  of  the 
chemical  with  which  it  is  coated. 

Speaking  of  appliances  used  on  board  ship  brings  to 
mind  a  rather  curious  little  appliance  for  automatically 
weighing  the  cargo  on  a  ship.  In  the  centre  of  the 
vessel  there  is  a  vertical  pipe,  or  shaft,  open  to  the  water 
at  the  bottom  end.  In  this  there  is  a  float  which  is 
connected  with  an  apparatus,  something  like  an  ordinary 
weighing-machine,  on  the  deck.  Of  course  the  water 
rises  in  the  shaft  as  the  vessel  sinks  down  under  its  load 
of  cargo,  and  the  float  striving  to  rise,  too,  indicates 
the  weight  on  board.  It  seems  at  first  sight  as  if  this 
would  do  just  as  well  hung  over  the  side  of  the  boat ; 
but  then  it  would  be  interfered  with  by  waves,  currents, 
and  the  movement  of  the  vessel,  whereas  in  this  small 
central  shaft  the  water  is  quite  still,  except  for  the  up 
and  down  motion  due  to  loading  and  unloading. 

The  name  of  this  appliance  is  "  porhydrometer,"  and 
it  is  mainly  useful  on  barges  and  such  small  craft.  It 
is  so  delicate  that,  on  a  2oo-ton  ship,  a  man  stepping  on 
or  off  will  make  a  difference. 

The  measuring  of  water  is,  of  course,  an  important 
matter,  especially  in  places  where  it  is  scarce  and  ex- 
pensive. At  waterworks  there  is  usually  a  meter  known 
by  the  name  of  "  venturi,"  which  records  automatically 
on  a  strip  of  paper  the  rate  at  which  the  water  is 
flowing  out.  The  principle  on  which  it  works  is  curious 
and  interesting.  In  the  main  pipe  there  is  placed  a 
narrow  neck,  and  it  follows  that  the  water  has  to  flow 
more  quickly  through  this  neck  than  it  does  in  the 
main  pipe.  Now,  observation  of  such  a  common 
thing  as  the  water  issuing  from  an  ordinary  garden- 
hose  will  show  us  that  water  in  rapid  motion  behaves 
differently  from  water  which  is  still  or  moving  slowly. 
The  water  in  the  hose-pipe  is  under  pressure,  and  is 
trying  not  only  to  pass  along  the  pipe,  but  to  burst  it ; 


Measuring  to  a  Hair's   Breadth 

in  other  words,  it  is  exerting  forces  in  all  directions. 
The  water  which  issues  from  the  nozzle,  on  the  other 
hand,  has  force  in  one  direction  only — namely,  the 
direction  in  which  the  nozzle  is  pointed,  and  that  is 
how  it  comes  about  that  we  can  direct  the  jet  where 
we  want  it  to  go.  The  "  all-direction "  force  in  the 
pipe  is  due  to  the  pressure,  and  the  "  one-direction " 
force  in  the  jet  is  due  to  the  velocity  at  which  the 
water  is  travelling.  When  water  is  still  and  under 
pressure  the  force  in  all  directions  is  quite  uniform  ; 
but,  as  soon  as  it  moves,  the  force  due  to  velocity 
begins  to  grow  (in  one  direction)  and  the  forces  due 
to  pressure  correspondingly  diminish. 

Thus,  when  the  water  rushes  at  increased  speed 
through  the  neck  in  the  pipe,  the  pressure  at  that 
point  becomes  reduced  because  of  the  increased  speed. 
Indeed,  the  reduction  in  pressure  bears  a  definite  pro- 
portion to  the  speed.  Therefore,  if  a  pressure-gauge 
be  connected  to  the  large  part  of  the  main,  and  another 
to  the  neck,  they  will  show  different  pressures,  and  the 
difference  will  indicate  the  rate  at  which  the  water  is 
flowing  through  the  neck. 

This  meter,  then,  consists  simply  of  a  suitable  gauge 
for  measuring  this  difference,  and  recording  it  by  a 
movable  pen  upon  a  moving  strip  of  paper. 

That  tells  the  flow  in  gallons  per  hour,  but  there 
are  meters  of  another  kind  which  register  the  actual 
number  of  gallons  which  pass.  These  are  mostly 
constructed  like  little  steam-engines,  with  a  cylinder,  or 
cylinders,  and  pistons.  The  water  drives  them  as  it 
passes  through,  and  the  number  of  revolutions,  of 
course,  tell  the  quantity  which  has  passed.  A  clock- 
work mechanism  counts  the  revolutions  and  records 
the  quantity  on  a  dial. 

Electricity  is  generally  measured  by  the  magnetic 
force  which  it  generates.  Every  conductor  becomes  a 

312 


Measuring  to  a  Hair's   Breadth 

magnet  while  current  is  passing  through  it,  and  the 
strength  is  in  proportion  to  the  volume  of  the  current. 
The  magnetism  is  distributed  along  the  whole  length 
of  the  conductor,  and  at  any  one  point  it  is  consequently 
very  small ;  but  by  winding  the  conductor  round  into  a 
coil,  insulating  it  of  course  so  as  to  prevent  the  current 
taking  a  short  cut  from  one  turn  to  another  instead  of 
travelling  the  whole  length  of  the  conductor,  we  can 
concentrate  a  good  deal  of  it  within  a  limited  area. 
We  can  concentrate  it  still  further  by  putting  an  iron 
core  in  the  middle  of  the  coil,  when  practically  the 
whole  of  it  will  be  manifested  in  the  core,  and  that  is 
how  an  electro-magnet  is  built  up.  Within  certain 
limits,  however,  the  fact  remains  that  whether  it  be  a 
single  straight  wire  or  an  electro-magnet  the  magnetic 
power  will  be  in  proportion  to  the  quantity  of  current 
passing.  If,  then,  we  take  an  electro-magnet  and  place 
near  to  it  a  piece  of  iron,  or  another  magnet  which  is 
able  to  move  except  that  it  is  held  back  by  a  spring, 
the  amount  by  which  it  is  pulled  and  the  spring 
stretched  will  tell  us  the  quantity  of  current  flowing. 
That  is  the  principle  of  the  ammeter,  the  instrument 
which  shows  the  number  of  amperes. 

Now  we  know,  from  an  earlier  chapter,  that  the 
quantity  of  current  which  flows  against  any  given 
resistance  depends  upon  the  pressure.  Consequently, 
if  we  couple  together  an  instrument  like  an  ammeter 
with  a  coil  of  fine  wire  offering  a  high  resistance,  and 
let  current  pass  through  both  in  succession,  the  instru- 
ment will  tell  us  the  quantity  which  passes,  and  if 
we  know  the  amount  of  resistance  we  shall  be  able 
to  tell  the  pressure. 

This  can  be  made  clearer  by  an  example.  Suppose 
we  want  to  find  the  pressure  of  the  current  flowing  in 
a  wire.  We  tap  that  wire  at  some  convenient  point  by 
connecting  another  branch-wire  to  it,  and  we  lead  the 

313 


Measuring  to  a  Hair's  Breadth 

current  from  the  branch  to  an  ammeter,  and  thence 
through  a  resistance-coil  back  to  the  return  (or  negative) 
wire,  or  to  the  earth  if  there  is  not  one.  Suppose,  too, 
that  we  make  the  resistance-coil  of  such  a  size  that  the 
total  resistance  in  the  branch  circuit  shall  be  200  ohms. 
Then  we  look  at  the  ammeter  and  see  that  one  ampere 
is  passing.  Now  one  volt  pressure  acting  against  one 
ohm  resistance,  causes  a  current  of  one  ampere  ; 
therefore,  to  produce  one  ampere  against  200  ohms 
must  need  200  volts,  from  which  we  see  that  the 
pressure  in  the  main  wire  must  in  this  instance  be 
200  volts.  As  a  matter  of  fact,  the  instrument  would 
in  practice  be  so  marked  as  to  show  us  the  number  of 
volts  straight  away.  A  voltmeter,  therefore,  is  the 
same  as  an  ammeter,  except  that  the  dial  is  marked 
differently  and  it  is  not  connected  up  in  the  main 
circuit,  but  in  a  branch  (or  shunt,  to  use  the  technical 
term)  in  series  with  a  resistance. 

An  ohmmeter  is  the  converse  of  a  voltmeter.  A 
current  of  known  pressure  is  generated  by  a  battery 
or  small  dynamo,  and  the  quantity  which  flows  through 
any  circuit,  under  the  influence  of  that  pressure,  shows 
the  resistance  of  the  circuit. 

There  is  another  common  unit  of  measurement  used 
for  electricity,  the  "watt,"  which  represents  the  actual 
amount  of  work  that  the  current  is  capable  of  doing. 
It  is  found  by  multiplying  together  the  current  strength 
in  amperes  and  the  pressure  in  volts.  For  instance, 
50  amperes  at  200  volts  is  10,000  watts,  or,  as  it 
is  often  expressed,  10  kilowatts.  This  term  is  often 
used  to  express  the  size  of  dynamos.  To  say  a 
200-volt  dynamo,  would  convey  no  idea  of  the  size 
of  the  machine,  nor  would  it  be  any  more  definite 
to  call  it  a  5o-ampere  dynamo.  Call  it  10  kilowatt, 
however,  and  you  give  its  size  at  once — its  coils  may 
be  wound  with  wire  in  such  a  way  as  to  produce  100 

314 


Measuring  to  a  Hair's   Breadth 

amperes  at  100  volts,  or  20  at  500,  but  it  will  be  the 
same  size  of  machine,  will  require  the  same  power  to 
drive  it,  and  will  do,  theoretically  at  any  rate,  the  same 
amount  of  work  either  in  lighting,  heating,  or  driving. 
The  name  "  Watt "  is  given  by  way  of  a  tribute  to  the 
memory  of  the  father  of  the  modern  steam-engine. 

A  thousand  watts  (or  a  kilowatt)  for  one  hour  con- 
stitute the  Board  of  Trade  unit  by  which  electric 
current  is  bought  and  sold.  It  is  measured  by  elec- 
tricity meters,  which  are  really  small  and  very  feeble 
electro-motors,  just  powerful  enough  to  turn  a  clock- 
work counting  mechanism,  and  arranged  so  that  the 
speed  shall  vary  with  the  current. 

This  chapter  could  be  prolonged  almost  indefinitely, 
but  I  must  mention  some  very  interesting  devices  for 
measuring  heat  in  places  where  an  ordinary  thermo- 
meter would  be  useless. 

Take  the  case  of  the  upper  part  of  a  blast-furnace. 
No  ordinary  thermometer  could  survive  the  heat  there, 
nor  could  any  one  get  near  enough  to  read  it,  but  it  so 
happens  that  the  electrical  conductivity  of  a  wire  varies 
with  the  temperature.  If,  then,  a  wire,  through  which 
electricity  is  passing,  be  introduced  into  the  furnace, 
the  reduction  in  the  current  will  indicate  the  increase 
in  resistance  which  in  turn  tells  the  heat. 

If  two  wires  of  different  metals  be  joined  together 
into  a  loop,  and  the  heat  at  one  of  the  joints  be  raised 
above  that  at  the  other  joint,  a  current  of  electricity 
will  be  generated  in  the  loop.  The  amount  of  that 
current  will  vary,  too,  in  proportion  to  the  difference 
in  heat  between  the  two  joints,  forming  another  means 
by  which  the  heat  at  some  inaccessible  spot  can  be 
measured  and  read  off  at  a  safe  distance.  Of  course 
these  methods  are  both  useless  in  such  a  place  as  the 
furnace  itself,  since  the  heat  would  destroy  the  wire, 
but  they  are  often  very  useful. 


Measuring  to  a  Hair's  Breadth 

The  heat  of  a  powerful  furnace  is  sometimes  ascer- 
tained by  the  simple  but  effective  method  of  placing  in 
it  a  series  of  bars  made  of  different  alloys,  and  noting 
which  of  them  melt  and  which  resist  the  heat. 

The  last  measuring  appliance  which  I  propose  to 
refer  to  is  that  for  ascertaining  the  power  of  a  steam- 
engine.  It  is  called  a  steam-engine  indicator,  and 
consists  of  a  small  cylinder  with  a  piston  inside  it 
held  down  by  a  spring.  The  lower  end  of  this  small 
cylinder  is  connected  by  a  pipe  with  one  end  of  the 
engine  cylinder,  and  the  pressure  of  steam  in  the  latter 
lifts  the  small  piston  against  the  force  of  the  spring. 
The  extent  to  which  the  small  piston  is  moved  by  the 
steam  indicates,  of  course,  the  pressure  of  steam  in  the 
engine  cylinder,  and  by  an  arrangement  of  levers  this 
movement  is  made  to  draw  a  diagram  on  a  moving 
piece  of  paper.  In  other  words,  the  engine  is  made  to 
write  down  its  own  character. 

From  this  diagram  it  is  easy  to  calculate  the  pressure 
per  square  inch  which  the  steam  exerts  against  the 
piston  in  the  engine  cylinder. 

Now  the  power  of  a  steam-engine  is  usually  stated  to 
be  so  many  "  indicated  horse-power,"  and  a  horse-power 
is  the  power  required  to  lift  33,000  Ibs.  one  foot  high 
(or  the  equivalent)  in  a  minute.  Thus,  suppose  we  had 
an  engine  the  area  of  whose  piston  was  100  square  inches, 
and  the  indicator  showed  the  pressure  to  be  60  Ibs.  per 
square  inch,  the  steam  would  obviously  push  the  piston 
with  a  force  of  6000  Ibs.  Suppose,  further,  that  the  piston 
moves  a  foot  at  each  stroke  and  makes  200  strokes  per 
minute,  it  will  then  move  200  feet  in  every  minute. 

Therefore,  we  can  see  that  this  engine  will  do  work 
equal  to  lifting  6000  Ibs.  200  feet  in  a  minute.  This 
would  be  spoken  of  as  1,200,000  foot-pounds,  and,  since 
33,000  foot-pounds  make  one  horse-power,  the  power 
of  our  engine  would  be  36  J  horse-power. 

316 


Measuring  to  a  Hair's  Breadth 

Gas-engines,  and  occasionally  steam-engines,  are 
described  as  being  of  so  many  brake  horse-power 
(often  written  B.H.P.),  in  which  case  a  brake  is  ap- 
plied to  the  fly-wheel  and  the  actual  amount  of  work 
which  the  engine  is  capable  of  doing  is  calculated  by 
that  means. 


317 


CHAPTER  XXIV 

LIFTING  AND   CONVEYING  MACHINERY 

POLITICAL  economists  tell  us  that  all  labour,  other 
than  mental,  consists  in  moving  matter  from  one 
place  to  another.  If  this  is  so,  it  is  evident  what  an 
important  part  in  the  economy  of  the  world  must  be 
played  by  those  appliances  whose  chief  purpose  is  the 
lifting  and  conveying  of  goods  and  materials.  Nothing, 
too,  serves  to  illustrate  more  clearly  the  recent  progress 
of  engineering  than  the  rapid  development  of  this  class 
of  machinery. 

It  will  be  interesting  to  start  with  an  appliance  the 
usefulness  of  which  is  specially  appreciated  by  the 
general  public — the  passenger-lift.  Not  long  ago  there 
were  but  few  of  these  and  they  were  nearly  all 
hydraulic,  but  to-day  they  are  everywhere  and  most  of 
them  are  electric.  This  is  not  unnatural,  for  electricity 
is  to  be  had  in  most  places  from  a  public  supply,  while 
hydraulic  power  generally  necessitates  a  steam-pump 
and  a  large  hydraulic  accumulator.  The  compact  little 
electric  motor,  too,  is  much  more  easily  found  room 
for  than  the  long  hydraulic  cylinder.  Electricity, 
moreover,  makes  safeguards  possible  which  were  un- 
known in  the  older  lifts.  A  modern  "  push-button  " 
lift,  for  example,  may  be  left  entirely  unattended,  and 
a  child  may  play  in  it  with  safety.  For  the  car  will 
resolutely  refuse  to  move  until  all  the  gates  are  shut, 
and  no  gate  will  allow  itself  to  be  opened  unless  there 
is  the  car  just  level  with  it.  If  you  are  on  a  floor 


Lifting  and  Conveying  Machinery 

where  the  car  is  not,  you  push  a  button,  and  in  a  few 
moments  the  car  comes  to  your  floor  and  stops  for 
you.  Then  you  open  the  gate  and  enter.  After 
closing  the  gate  behind  you,  you  push  one  of  a  row  of 
buttons  in  the  car,  one  for  each  floor,  and  the  car  then 
goes  up  or  down  as  the  case  may  be,  to  the  floor 
whose  button  you  pushed.  If  you  and  another  man 
push  buttons  simultaneously,  the  lift  does  not  hesitate, 
but  serves  the  one  who,  according  to  a  prescribed 
"  table  of  precedence,"  has  the  first  claim.  A  scheme 
such  as  this,  while  by  no  means  difficult  to  arrange 
with  electricity,  would  be  almost  impossible  with  any 
other  power. 

The  precise  method  by  which  these  automatic  lifts 
are  controlled  is  too  intricate  to  describe  in  detail, 
but  the  general  principles  can  be  briefly  illustrated. 
The  motor  is  started  and  stopped  by  a  controller, 
a  piece  of  mechanism  with  which  we  are  already 
familiar,  only  instead  of  being  operated  by  hand,  like 
the  controller  of  a  tramcar,  for  example,  the  lift-con- 
troller is  worked  by  a  series  of  magnets  which  are 
energised  by  the  currents  which  pass  through  the 
"  push-buttons." 

The  current  from  each  button  passes  through  a 
switch  on  each  of  the  gates,  which  is  only  making 
contact  when  the  gate  is  properly  closed.  If  any  one 
of  the  gates  is  open,  therefore,  all  the  buttons  are 
thrown  out  of  operation,  for  no  current  can  pass  from 
them,  and  the  car  cannot  be  moved.  At  the  same 
time  there  is  a  lock  on  each  gate  which  is  only  released 
by  the  car  standing  opposite  to  it. 

The  actual  lifting  and  lowering  mechanism  of  an 
electric  lift  is  fairly  simple.  The  motor  turns  a  screw, 
the  threads  of  which  engage  in  the  teeth  of  a  tooth- 
wheel.  This  combination  of  a  screw  and  a  tooth-wheel 
constitutes  what  is  known  as  "  worm-gearing,"  the 

3*9 


Lifting  and  Conveying  Machinery 

screw  being  the  "  worm/'  a  name  probably  derived 
from  the  wriggling  appearance  which  it  presents  when 
it  is  revolving.  The  wheel,  in  turn,  drives  a  small 
barrel,  around  which  wire-rope  is  wound.  One  end  of 
this  rope  passes  over  a  wheel  and  supports  the  car,  while 
the  other  end  passes  over  another  wheel  and  supports 
the  balance-weight.  When  the  barrel,  then,  is  turned 
(in  one  direction)  it  winds  up  the  car,  and  it  is  assisted 
by  the  balance-weight  pulling  at  the  other  end  of  the 
rope.  Consequently,  it  only  has  to  lift  the  amount  by 
which  the  car  and  its  load  exceeds  the  balance-weight. 
When  turned  the  other  way  it  lifts  the  weight  and 
lowers  the  car. 

As  a  matter  of  fact  the  motor  often  has  to  exert  its 
power  in  order  to  bring  the  car  down.  It  would  appear 
to  be  the  correct  thing  to  make  the  weight  just  balance 
the  car,  so  that  all  the  motor  would  have  to  do  would 
be  to  lift  the  load  in  the  car.  The  practice,  however, 
is  to  make  the  weight  balance  the  car  and  half  the 
maximum  load  as  well.  This  is  a  very  clever  device, 
the  advantage  of  which  can  best  be  made  clear  by  an 
example.  Suppose  a  car  weighs  half  a  ton  and  the 
maximum  load  is  6  cwts.,  and  let  us  take  the  case 
of  a  full  load  going  up  and  the  car  coming  down  again 
empty. 

If  the  weight  balances  the  car,  the  motor  has  to  lift 
6  cwts.  on  the  up  journey,  and  on  the  down  journey 
it  has  to  lift  nothing. 

Now  see  the  difference  if  half  the  load  is  balanced  as 
well.  The  motor  then  has  to  lift  only  3  cwts.  on 
the  upward  trip,  but  it  has  to  lift  3  cwts.  of  bal- 
ance-weight as  the  empty  car  descends.  The  same 
total  amount  of  power,  then,  is  expended,  and  it 
may  well  be  asked  :  Where  does  the  advantage 
come  in  ? 

In  the  first  case  the  motor  may  be,  and  often  is, 

320 


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II 


Lifting  and  Conveying  Machinery 

called  upon  to  lift  6  cwts.,  but  in  the  second 
case  it  can  never  be  called  upon  to  lift  more  than 
3  cwts.  Consequently,  a  motor  of  approximately 
half  the  size  will  do.  The  net  result  of  this  in- 
genious arrangement  is,  then,  that  at  a  cost  of 
3  cwts.  of  balance  weight  (a  mere  nothing)  a  con- 
siderable saving  can  be  effected  in  the  cost  of  the 
motor  and  gearing,  and  the  whole  concern  is  materi- 
ally cheapened. 

Nervous  passengers  may  be  comforted  to  hear  that 
there  are  ample  safeguards  against  accidents  in  all 
passenger  lifts.  The  car,  it  will  be  noticed,  slides 
between  two  guides,  and  there  is  a  powerful  spring  clip 
which  grips  these.  It  is  only  the  pull  on  the  ropes 
which  keeps  this  clip  open,  so  that  if  they  should  break, 
the  car  would  not  fall  to  the  bottom,  but  would  be 
instantly  held  stationary  by  this  clip. 

Of  cranes  there  is  an  almost  endless  variety,  many 
of  them  designed  and  constructed  for  some  special 
purpose.  An  interesting  example  of  these  is  the 
"  Titan  "  crane,  largely  used  for  setting  the  concrete 
blocks  used  in  the  construction  of  breakwaters.  One  of 
them  is  shown,  facing  page  320,  actually  lowering  a 
block  into  position. 

Modern  breakwaters  are  almost  always  built  of  these 
concrete  blocks.  They  are  made  of  shingle  and 
Portland  cement  cast  in  a  wooden  mould,  and  are 
brought  to  the  site  either  in  barges  or  on  trucks. 
They  are  very  large,  weighing  perhaps  50  tons  each, 
and  are  built  up  into  the  wall  just  like  huge  bricks,  so 
that  we  may  look  upon  these  "  Titan "  cranes  as 
gigantic  mechanical  bricklayers.  Now  cranes  capable 
of  handling  such  heavy  weights  as  50  tons  need  a 
firm  support  to  stand  upon,  and  the  great  advantage  of 
this  type  is  that  it  can  stand  upon  that  part  of  the  wall 
which  is  already  finished.  First  there  is  a  very  strong 

321  x 


Lifting  and  Conveying  Machinery 

carriage,  which  runs  upon  railway  wheels,  so  that  it 
can  be  moved  forward  as  the  work  proceeds.  This 
carriage  supports  a  great  horizontal  beam,  one  end  of 
which  stretches  out  a  long  way,  while  the  other  end 
overhangs  but  little.  On  the  long  end  there  are  rails, 
upon  which  runs  a  small  but  very  strong  truck,  from 
which  depends  the  rope  which  lifts  the  blocks.  At  the 
other  end  is  a  heavy  weight,  frequently  a  mass  of 
concrete,  to  balance,  partially,  the  weight  of  the  block, 
and  for  the  same  reason  the  engine,  boiler,  and  machinery 
are  placed  there  also.  The  great  beam,  with  its 
balance  weight,  machinery,  and  its  load  too,  can  swing 
right  round  as  if  it  were  pivoted  upon  the  top  of  the 
carriage. 

Its  method  of  working  is  this.  First  it  lowers  a 
diving-bell  on  to  the  sea  floor,  the  workmen  inside  the 
bell  levelling  the  ground  and  making  ready  for  the 
block.  Then  the  bell  is  drawn  up  and  the  massive 
arm  swings  round  to  pick  up  the  block.  It  stops  over 
where  the  block  is,  either  in  a  truck  on  the  breakwater 
behind  it  or  in  a  barge  alongside ;  the  truck  on  the 
beam  is  run  out  or  drawn  back  (of  course  all  the 
movements  are  done  by  the  steam-engine)  until  it,  too, 
is  over  the  block,  and  then  the  rope  is  let  out  and 
hooked  on.  Quickly  the  5<D-ton  mass  of  concrete 
rises  in  the  air,  the  arm  swings  round,  the  truck  travels 
to  the  correct  position,  and  down  goes  the  block  into 
the  water,  just  in  the  right  place,  to  be  finally  adjusted 
by  divers  working  below. 

It  is  obvious,  however,  that  only  one  of  these  cranes 
can  work  at  a  time  on  one  breakwater,  so  where  it  is 
very  large  two  parallel  "  gantries "  are  built — long, 
narrow  stages,  one  on  each  side  of  where  the  break- 
water is  to  be.  They  are  constructed  of  piles  and 
beams,  and  along  the  top  of  each  is  a  line  of  rails, 
supporting  several  cranes  of  another  kind,  known  as 

322 


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Lifting  and  Conveying  Machinery 

"  Goliaths."  These  consist  each  of  a  pair  of  girders, 
placed  parallel  to  each  other,  and  supported  at  their 
ends  upon  legs  which  have  wheels  capable  of  running 
on  the  rails.  The  girders  therefore  span  across  the 
site  of  the  breakwater,  one  end  resting  by  means  of 
its  "  legs  "  on  each  of  the  "  gantries."  On  the  girders 
there  is  a  truck  supporting  the  winch  which  raises  and 
lowers  the  blocks.  The  winch  on  its  truck  can  travel 
to  and  fro  along  the  girders,  and  the  whole  structure 
can  travel  along  the  gantries,  so  that  the  winch  can 
be  brought  over  any  desired  spot.  These  cranes  can 
be  driven  by  steam-power  or  electricity,  whichever  is 
most  convenient,  and  several  of  them  can  work 
simultaneously  at  different  positions  along  the  same 
gantry. 

A  similar  crane,  but  without  the  legs,  its  girders 
resting  directly  upon  wheels  which  run  on  the  gantries, 
can  be  seen  in  most  factories  where  heavy  objects  have 
to  be  moved  frequently,  and  in  most  engine-houses 
for  handling  the  heavy  parts  of  the  engines  during 
erection  or  when  under  repair.  These  cranes  are 
called  "  overhead  travellers."  They  are  being  largely 
used,  too,  in  shipyards,  the  two  gantries  being  placed 
one  on  each  side  of  the  ship  under  construction,  so 
that  the  cranes  can  quickly  haul  up  plates,  ribs,  or 
other  parts,  and  place  them  in  position.  They  can 
also  be  used  for  holding  the  hydraulic  riveting 
machines.  Several  overhead  travellers  can  work  on 
the  same  pair  of  gantries. 

A  very  useful  form  of  lifting  appliance  is  the  "trans- 
porter," which  is  very  largely  used  for  loading  and 
unloading  ships  with  such  cargoes  as  coal  and  ore.  It 
consists  of  a  long  steel  beam,  supported  upon  tall 
trestles.  On  this  beam  there  runs  a  small  trolley,  which 
is  hauled  backwards  and  forwards  by  machinery  at  one 
end.  From  this  trolley  hangs  a  rope,  to  which  can  be 

323 


Lifting  and  Conveying  Machinery 

attached  a  bucket  or  a  "grab."  One  end  of  the  beam 
is  often  made  to  overhang  the  water,  so  that  the  trolley 
can  run  right  out  over  the  ship  and  lower  the  grab 
or  bucket  right  down  into  the  hold.  Then  when  it  is 
filled  it  is  hauled  up,  and  the  trolley  runs  back  with  its 
load  towards  the  other  end  of  the  beam.  These  work 
very  quickly,  and  all  the  movements  are  easily  con- 
trolled by  one  man,  who  is  stationed  in  a  small  cabin 
placed  at  a  suitable  spot,  where  he  can  observe  easily 
what  is  going  on. 

Sometimes  a  rope  is  used  instead  of  a  beam,  and  the 
apparatus  is  then  called  a  "  Blondin."  One  of  these 
was  much  talked  about  some  years  ago  in  connection 
with  the  erection  of  the  bridge  over  the  Zambesi  near 
the  Victoria  Falls.  A  great  part  of  the  material  used 
was  carried  from  one  side  of  the  river  to  the  other  by 
this  means. 

This  brings  us  to  what  is  perhaps  the  most  wonderful 
conveying  appliance  in  existence,  of  course  excepting 
the  railway — the  aerial  ropeway.  Districts  which  can 
scarcely  be  traversed  by  any  living  creature,  and  which 
are  so  mountainous  and  rugged  as  to  be  quite  imprac- 
ticable for  an  ordinary  railway,  are  crossed  quite  easily 
by  these  "  railways  in  the  air." 

Essentially  a  ropeway  consists  of  a  long  wire  rope, 
with  its  two  ends  spliced  together  so  as  to  form  an 
endless  loop,  which  is  stretched  round  two  large  wheels 
or  drums  and  supported  at  intervals  on  smaller  wheels. 
The  large  wheels  may  be  several  miles  apart,  and,  one 
of  them  being  turned  round,  the  rope  is  made  to  travel 
at  a  rate  of  about  four  or  five  miles  per  hour.  Buckets 
are  hung  upon  this  moving  rope  at  intervals — not 
attached  to  it,  observe,  but  simply  hung  on,  by  means 
of  an  ingenious  clip.  This  clip  keeps  them  from 
slipping  off  or  sliding  along  even  when,  as  is  often  the 
case,  the  rope  rises  at  a  very  steep  angle,  yet  it  lets  go 


II 


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Lifting  and  Conveying  Machinery 

the  rope  instantly,  when  the  bucket  reaches  the  end  of 
the  journey. 

Each  of  the  large  wheels  is  mounted  in  a  substantial 
framework,  known  as  a  "  terminal  frame/'  and  one  of 
them  is  adjustable,  so  that  the  rope  can  be  pulled  to 
the  requisite  degree  of  "  tautness."  The  frame  also 
supports  a  "  shunt  rail,"  a  sort  of  siding  on  to  which 
each  bucket  as  it  arrives  is  shunted,  to  be  loaded  or 
unloaded,  as  the  case  may  be.  The  "  hanger "  by 
which  each  bucket  is  suspended  not  only  carries  the 
little  clip  already  referred  to,  but  also  two  small 
grooved  rollers.  The  shunt  rail  is  in  the  form  of  a 
loop,  one  end  of  which  forms  a  junction  with  the 
incoming  part  of  the  rope  and  the  other  with  the 
outgoing  part,  and  the  rope  is  so  guided  by  wheels 
that  just  as  it  passes  the  first  junction  it  dips  down  and 
leaves  the  bucket  supported,  by  means  of  the  rollers, 
on  the  shunt  rail.  The  bucket  is  loaded  or  unloaded, 
and  then  pushed  along  by  hand  to  the  other  junction, 
where  it  runs  on  to  the  outgoing  rope  and  is  carried 
back  to  the  other  end.  Thus  the  buckets  come  in 
in  regular  succession,  and,  as  regularly,  are  sent 
back. 

Between  the  two  terminals  the  rope  is  supported  by 
wheels  fixed  on  tall  trestles  of  steel  or  timber.  The 
wheels  have  grooves  in  them  in  which  the  rope  runs, 
deep  enough  to  keep  it  from  slipping  off,  but  not  so 
deep  as  to  interfere  with  the  clips  which  grasp  the 
upper  side  of  the  rope. 

Although  buckets  have  been  referred  to  above,  other 
receptacles  can  be  used  instead  if  the  material  to  be 
conveyed  necessitates  it,  such  as  cradles,  for  example, 
for  carrying  timber.  Ropeways,  moreover,  do  not 
always  require  to  be  driven.  Sometimes  when  the 
loading  end  is  higher  than  the  unloading  end,  the 
loaded  buckets  descending  on  one  side  pull  up  the 

325 


Lifting  and  Conveying  Machinery 

empty  ones  the  other  side.  Nay  more,  when  the 
difference  in  level  is  great  enough,  the  ropeway  may 
actually  have  energy  to  spare  which  can  be  used  to 
drive  other  machinery. 

Some  of  these  lines  are  as  much  as  10  miles  long. 


326 


Ky  permission  of 


AN  AERIAL  ROPEWAY 


Kopeways,  Ltd. 


It  is  shown  crossing  a  wild  rockj?  valley  where  other  means  of  transport 
is  well-nigh  impossible. 


CHAPTER   XXV 

PROTECTION   FROM   FIRE 

IN  the  original  scheme  of  this  book  I  did  not  put  down 
this  subject,  but  one  afternoon,  while  engaged  upon  one 
of  the  earlier  chapters,  I  chanced  to  look  out  of  the 
window  and  perceived  an  unusual  glare  in  the  sky. 
Soon  great  masses  of  flame  became  visible,  and  it  was 
evident  that  a  serious  fire  was  in  progress  not  far 
away. 

It  turned  out  to  be  a  very  large  block  of  shops  filled 
with  drapery,  furniture,  and  other  inflammable  matter, 
and  situated  amid  rows  of  houses,  and  actually  adjoin- 
ing some.  When  I  reached  the  scene  of  the  fire,  the 
whole  block  of  buildings  was  blazing  from  top  to 
bottom.  The  heat  could  be  felt  a  hundred  yards 
away,  and  there  seemed  to  be  no  hope  whatever  of 
saving  the  adjoining  houses. 

Yet  within  an  hour  the  fire  was  practically  out  and 
the  houses  uninjured. 

This  struck  me  as  being  such  a  remarkable  triumph 
for  the  engineer,  in  the  extinguishing  appliances,  that 
I  decided  to  include  this  chapter.  If,  however,  the 
building  had  been  built  on  modern  "  fire-resisting " 
principles,  the  fire  would  probably  never  have  reached 
serious  proportions  at  all. 

In  large  buildings,  the  framework  is  almost  always 
mainly  of  iron  or  steel.  Where  space  is  scarce  and 
of  fabulous  value,  as  it  is  in  some  populous  cities,  the 
buildings  cannot  be  extended  horizontally,  so  they  have 

327 


Protection  from  Fire 

to  expand  upwards.  The  number  of  floors  must  be 
increased.  Now,  every  extra  floor  means  more  weight 
to  be  supported,  and  if  brick  walls  were  the  only 
supports  available  a  very  tall  building  would  be  im- 
practicable, for  the  walls  would  need  to  be  so  thick 
that  there  would  be  scarcely  any  useful  space  left  at 
the  ground  level.  The  high  building,  therefore,  called 
into  being  the  steel  frame,  in  which  each  floor  is 
formed  of  a  network  of  steel  girders  supported  on 
vertical  steel  columns,  the  brick  walls  having  little  to 
do  except  to  keep  the  weather  out. 

Now,  strange  as  it  may  appear,  a  heavy  beam  of 
wood  resists  fire  better  than  a  steel  girder.  The 
surface  of  the  wood  beam  becomes  burnt,  leaving  a 
layer  of  charred  wood  which  protects  the  rest  of  the 
beam.  Thus  while  it  is  weakened  somewhat,  it  still 
retains,  in  all  probability,  sufficient  strength  to  do  its 
work.  Steel,  on  the  other  hand,  if  unprotected,  while 
it  does  not  burn,  becomes  so  softened  by  the  intense 
heat  of  a  great  fire,  that  it  bends  like  lead.  After  the 
fire  referred  to  just  now  there  were  to  be  seen  heavy 
steel  beams  bent  into  the  most  fantastic  shapes,  show- 
ing how  they  had  been  softened  by  the  heat. 

A  steel-framed  building  is  not  therefore  necessarily 
fireproof ;  to  make  it  so  the  steelwork  must  be  pro- 
tected in  some  way. 

The  use  of  iron  il joists"  for  forming  the  floors 
came  in  before  the  time  of  steel  frames,  and  it  was 
soon  followed  by  the  use  of  concrete  to  fill  in  between 
them.  The  concrete,  however,  did  not  always  require 
to  be  as  deep  as  the  joists,  and  so  the  under  side  of  the 
latter  was  left  at  the  mercy  of  a  fire  on  the  floor  below. 
To  get  over  this  difficulty  several  patent  systems  were 
invented,  most  of  which  used  firebrick  tiles,  which 
spanned  the  space  between  the  joists,  and  not  only 
supported  the  concrete  of  the  floor  until  it  had  set, 

328 


Protection  from   Fire 

but  also  covered  entirely  the  under  side  ]of  the  joists, 
forming  in  some  cases  a  clear  space  underneath  them, 
so  that  the  fire  should  be  effectively  prevented  from 
touching  the  iron.  The  concrete,  by  the  way,  which 
is  used  for  fireproof  floors  is  often  made  of  "  coke 
breeze,"  as  it  is  called — fine  coke — which,  strange  to  say, 
on  being  mixed  with  cement  ceases  to  be  a  good  fuel 
and  becomes  an  excellent  fire-resisting  material,  while 
its  weight  is  considerably  less  than  other  kinds  of 
concrete. 

After  that,  it  soon  became  the  custom  to  encase  the 
iron  uprights  as  well  in  some  fireproof  material — 
frequently  concrete — resulting  in  the  complete  fire- 
resisting  buildings  of  the  present  day. 

Meanwhile,  from  other  causes,  another  kind  of  build- 
ing material  had  come  to  the  front,  which,  in  addition 
to  its  other  qualities,  is  perfectly  fire-resisting.  It  is 
known  as  " ferro-concrete  "  or  "reinforced  concrete," 
and  is  steel  and  concrete  in  intimate  combination.  It 
may  seem  strange  to  call  this  new,  for  concrete  was 
known  to  the  ancients,  and  iron  has  been  used  in 
buildings  for  years.  They  had  been  used  together, 
too,  as  in  the  concrete  floors  described  above,  but  they 
had  never  been  used  in  combination,  so  that  under  those 
conditions  they  formed  what  may  quite  correctly  be 
called  the  newest  building  material. 

As  explained  in  the  chapter  on  bridges,  the  strength 
of  a  beam  consists  in  the  power  of  its  upper  part  to 
resist  compression  and  its  lower  part  to  resist  tension. 
Now  concrete  is  excellent  for  the  former  purpose  and 
steel  for  the  latter,  so  that  a  beam  made  of  concrete, 
with  steel  bars  embedded  in  its  lower  part,  to  resist  the 
tensile  stresses,  is  very  strong.  When  loaded  it  exhibits 
a  remarkable  degree  of  elasticity,  bending  slightly,  but 
returning  to  its  original  form  when  the  load  is  removed 
— a  condition  of  things  which  is  absolutely  necessary  in 

329 


Protection  from  Fire 

any  lasting  structure.  It  appears  to  be  subject  to  no 
form  of  decay,  for  the  cement  has  the  power  of  com- 
pletely preserving  the  steel  from  rust ;  indeed  if  the 
bars  be  rusty  when  put  in,  the  cement  combines 
chemically  with  the  rust  and  entirely  removes  it :  very 
different  from  the  action  of  paint,  for  if  paint  be  put  on 
rusty  iron  the  rusting  process  still  goes  on  under  the 
paint,  and  is  all  the  more  serious  because  it  is  unseen. 

Ferro-concrete    is  also,   as  has  been  said,  perfectly 
fire-resisting,  and  as  it  is  built  up  continuously  a  build- 


Section  through  beam. 


FIG.  45. — Reinforced  concrete  beam,  supported  on  two  reinforced  concrete 
columns ;  the  dotted  lines  show  the  "  reinforcement "  of  steel  rods. 

ing  constructed  of  it  becomes  what  is  called  "  mono- 
lithic," one  single  piece  of  ferro-concretc,  without  a 
joint,  from  top  to  bottom. 

Wooden  moulds  have  to  be  constructed  in  which  to 
form  the  various  parts.  When  it  is  a  beam,  the  steel 
bars  are  laid  in  the  bottom  of  the  mould  and  the 
concrete  filled  in  around  and  above  them.  The  up- 
rights are  made  in  just  the  same  way,  except  that  the 
bars  are  placed  at  the  corners.  Each  part  is  thus 
moulded  in  position,  and  when  the  concrete  has  set  the 
timber  is  taken  away.  There  are  several  special  forms 
of  bars  used  for  this  purpose,  the  idea  being  to  give 
them  such  a  shape  that  the  concrete  will  grip  them 

330 


Protection  from  Fire 

securely  ;  but  it  seems  as  if  smooth  round  steel  bars 
answer  as  well  as  anything,  the  cement  having  a 
power  of  adhesion  to  smooth  steel  which  is  positively 
astounding. 

Thus  we  see  that  a  modern  "  fire-proof "  (or,  to  use 
a  more  accurate  term,  "  fire-resisting  ")  building  has  all 
its  floors,  main  walls,  and  supports  formed  in  such  a 
way  that  not  only  will  they  not  burn,  but  they  will 
not  be  seriously  weakened  by  heat.  The  interior  fittings 
may  be  of  wood,  and  the  rooms  may  be  filled  with 
inflammable  material,  but  should  they  catch  fire  the 
building  itself  will  stand  secure,  and  most  probably  the 
fire  can  be  confined  to  the  room  in  which  it  starts. 

When  the  fire  is  thus  hemmed  in  by  walls  and  floors 
of  fire-resisting  material,  there  is  still  need  of  fire- 
extinguishing  appliances  to  put  it  out.  A  device  of 
this  nature  which  is  often  installed  in  factories  and 
warehouses  is  called  a  "  sprinkler."  It  consists  of  a 
nozzle  fixed  in  the  centre  of  the  ceiling,  if  the  room 
is  a  small  one,  or  several  distributed  about  in  the  case 
of  a  large  room,  connected  by  pipes  either  to  a  tank 
high  up  upon  the  roof,  or  in  which  water  is  stored 
under  pressure.  Normally  each  nozzle  is  closed  by 
a  specially  devised  plug,  which  is  held  in  place  by  a 
piece  of  lead  or  some  similar  metal.  As  soon,  then, 
as  a  fire  breaks  out  in  the  room,  it  melts  the  lead,  the 
plugs  are  released,  and  each  nozzle  sends  forth  a  spray 
of  water,  drenching  the  whole  contents  of  the  room,  and 
quickly  extinguishing  the  fire. 

Many  buildings,  too,  are  fitted  with  fire-alarms  which 
automatically  call  the  fire-brigade.  There  are  different 
varieties  of  these,  but  one  will  illustrate  the  principle 
on  which  most  of  them  work.  Imagine  an  ordinary 
mercury  thermometer,  but  with  two  wires  penetrating 
the  glass  tube.  One  of  these  is  low  down,  so  as  to  be 
always  in  contact  with  the  mercury,  while  the  other  is 

331 


Protection  from   Fire 

higher  up,  at  say  100°.  Thus  they  are  normally 
disconnected,  but  as  soon  as  the  temperature  of  the 
room  rises  to  the  prearranged  limit,  the  column  of 
mercury  reaches  the  higher  wire  and  connects  the  two 
electrically.  This  completes  a  circuit,  and  so  permits 
current  from  a  battery  to  flow,  ringing  a  bell  or  other 
alarm. 

But  the  best-known  and  most  interesting  of  all  fire- 
appliances  is  the  fire-engine.  He  must  be  a  very 
phlegmatic  person  who  does  not  feel  a  thrill  when  he 
hears  the  shouting  of  the  firemen,  and  sees  the  engine 
gallop  past.  Indeed,  some  people  appear  to  be  so 
moved  by  the  sight,  that  they  cannot  help  running 
after  the  engine,  though  they  cannot  possibly  keep  up 
with  it,  and  the  fire  may  be  miles  away. 

The  galloping  horses,  however,  are  gradually  being 
superseded  by  self-propelled  engines,  either  steam  or 
petrol,  and  the  hoarse  cries  of  the  men  are  giving  place 
to  a  loud-mouthed  bell. 

The  horsed  fire-engine  is  still  used,  though,  to  a  very 
large  extent,  and  deserves  a  description.  It  is  a  beauti- 
ful piece  of  engineering,  combining  great  power  in  a 
very  small  compass.  There  is  a  tiny  boiler,  which  is 
heated  by  a  coke  fire.  Behind  it  is  a  beautiful  little 
two-cylinder  vertical  engine  working  two  pumps.  Both 
engine  and  pumps  are  small,  but  they  work  at  a  high 
speed,  and  so  get  through  a  large  amount  of  work. 
The  two  large  brass  vessels  which  form  such  a  con- 
spicuous feature  on  a  fire-engine  are  air-vessels,  whose 
duty  is  to  act  as  spring  buffers,  and  equalise  the  flow 
of  water,  as  explained  in  an  earlier  chapter. 

The  engine  stands  in  the  station  with  the  fire  all 
laid  ready  for  lighting.  The  harness  is  all  attached, 
and  the  horse-collars  are  suspended  from  the  ceiling 
by  cords.  These  collars  are  in  halves,  hinged  together 
at  the  top  and  open  at  the  bottom,  so  that  they  hang 

332 


Protection  from  Fire 

like  an  inverted  letter  V,  and  do  not  need  to  be  put 
over  the  horses'  heads,  but  simply  drop  on  to  their 
necks,  and  all  that  has  to  be  done  is  to  close  the  two 
lower  ends  and  fasten  them  together  under  the  horse's 
chin,  as  it  were.  Each  horse  stands  in  a  stall  on 
its  own  side  of  and  within  a  few  feet  of  the  engine  ; 
thus  a  few  seconds  suffice  to  lead  out  the  horses,  drop 
the  collars  on  to  them,  fasten  the  latter,  and  then  all  is 
ready.  The  rushing  through  the  air  fans  the  fire,  and 
in  a  few  minutes  steam  is  up. 

The  steam  motor  fire-engine  is  very  like  the  horsed 
engine,  except  that  its  engine  (using  the  word  in  its 
proper  sense)  is  normally  connected  to  the  wheels,  but 
by  a  simple  arrangement  can  be  quickly  disconnected 
on  arrival  at  the  fire,  and  connected  to  the  pumps. 
Thus  the  same  mechanism  which  pumps  the  water 
propels  the  vehicle  to  the  scene  of  operations. 

It  is  clear  that  an  engine  of  this  type  must  always 
have  steam  up  ready  to  start.  The  fire  is  not  lit, 
however,  only  laid,  but  the  water  is  kept  hot  at  the 
station  either  by  a  large  gas  burner  or  a  special  stove. 

The  very  latest  type  of  all  is  the  petrol  fire-engine. 
This  is  really  a  very  strongly  made  motor-car,  able 
to  withstand  plenty  of  rough  travelling  without  likeli- 
hood of  breaking  down,  with  a  pump  mounted  upon 
it.  On  reaching  the  fire  the  motor  is  disconnected 
from  the  wheels  and  connected  to  the  pump  in  a 
few  seconds — more  quickly,  in  fact,  than  the  hose  can 
be  got  out  and  coupled  up. 

Some  fire-engines  carry  what  are  called  chemical 
cylinders,  by  which  a  jet  of  water  can  be  thrown 
instantly  the  fire  is  reached,  without  having  to  wait 
for  the  hose  to  be  connected  to  the  water-mains. 
The  cylinder  itself  is  full  of  water,  and  to  start  the 
jet  a  chemical  is  mixed  with  it.  This,  combining  with 
another  chemical  already  in  the  water,  causes  carbonic 

333 


Protection  from   Fire 

acid  gas  to  be  given  off.  The  evolution  of  the  gas 
creates  a  pressure  in  the  cylinder  enough  to  force 
the  jet  to  a  considerable  height.  Such  a  jet  is  a 
better  fire-extinguisher,  too,  than  ordinary  water,  for 
it  contains  carbonic  acid  gas  dissolved  in  it,  and  this 
gas,  as  is  well  known,  itself  has  a  damping  effect  on 
fire. 

The  hand  fire-extinguishers  which  are  often  hung 
up  in  public  buildings  for  use  in  an  emergency  are 
constructed  on  this  principle.  They  contain  water 
and  a  glass  vessel  holding  the  chemicals.  The  latter 
has  to  be  broken  by  a  blow,  and  then  the  apparatus 
is  ready  to  work. 


334 


CHAPTER   XXVI 
THE  CONQUEST  OF  THE  AIR 

SINCE  ancient  times  man  has  desired  to  emulate  the 
birds  and  insects  by  flying  in  the  air,  yet  only  within  the 
last  few  years  has  the  feat  been  accomplished.  The 
final  battles  in  the  struggle  between  man  and  the  air  have 
been  decided,  too,  with  astonishing  suddenness,  so  that 
quite  young  people  can  remember  the  time  when  "  to 
fly  "  was  the  proverbial  equivalent  for  the  impossible  ; 
yet  now  almost  every  day  sees  fresh  records  being  made 
in  this  astonishing  sport,  and  before  long,  no  doubt,  it 
will  pass  from  the  stage  of  a  sport  for  the  adventurous, 
and  become  one  of  the  recognised  features  of  our 
daily  life. 

The  means,  too,  by  which  success  has  been  achieved, 
is  quite  opposed  to  the  well-worn  theory  that  if  a  man 
wants  to  do  a  thing  he  must  imitate  Nature,  for  the 
flying-machine  has  in  many  of  its  features  no  counter- 
part among  the  birds  and  insects.  It  is  true  that  there 
is  a  certain  resemblance  between  a  monoplane  and  a 
bird,  when  it  is  soaring  with  outstretched  wings,  but 
there  is  certainly  no  natural  biplane  nor  is  there  any 
revolving  propeller  in  Nature,  or  indeed  any  rotary 
motion  at  all,  except  in  certain  very  low  forms  of 
insect  life. 

Thus  we  are  face  to  face  with  a  very  curious  problem. 
If  man's  ways  of  flying  are  the  best,  how  is  it  that 
Nature  has  not  adopted  them  ?  or  on  the  other  hand,  if 
Nature's  ways  are  the  best,  why  does  not  man  copy 

335 


The  Conquest  of  the  Air 

them  ?  This  is  a  very  interesting  subject  for  reflection, 
and  the  answer  seems  to  lie  along  one  of  two  lines,  or 
perhaps  along  both. 

Nature's  appliances  are  for  all-round  use,  and,  looked 
at  from  that  standpoint,  they  are  unrivalled.  As  a 
machine  for  running,  walking,  jumping,  crawling,  and 
swimming,  there  is  nothing  to  compare  with  the  legs  of 
a  lion,  for  instance.  They  will  take  their  owner  over 
rough  places  as  well  as  smooth,  up  steep  hills,  and  also 
along  level  ground,  up  trees  and  precipices  if  need  be. 
For  all-round  purposes  it  would  be  almost  impossible  to 
improve  upon  them,  yet  for  travelling  along  a  smooth 
and  level  road  the  inferior  strength  of  a  man  on  a  bicycle 
can  rival  the  speed  of  the  fastest  animal,  and  beat  most 
of  them  for  endurance  over  a  long  distance.  This,  too, 
is  only  one  example  of  many  which  might  be  brought 
forward,  which  seem  to  indicate  that  for  certain  special 
purposes  the  mind  of  man  is  capable  of  devising 
appliances  different  from,  and  sometimes  better  than, 
those  which  grow  naturally. 

The  second  answer  to  the  question  why  we  do  not 
always  imitate  Nature  is  this.  We  cannot.  Take  the 
case  of  a  bird's  wing.  It  is  a  piece  of  mechanism  which 
puts  to  shame  the  very  best  that  the  engineer  can  pro- 
duce. Many  attempts  have  been  made  to  produce  a 
machine  with  wings  which  flap  like  a  bird.  Some  very 
ingenious  and  clever  devices  have  been  made,  but  the 
friction  of  the  various  parts  has  in  every  case  been  such 
as  to  make  them  absolutely  worthless  for  practical 
purposes.  Compared  with  the  beautiful  mechanism  of 
the  bird's  wing,  they  are  crude,  clumsy,  and  inefficient 
in  the  extreme. 

It  seems  reasonable  to  say,  therefore,  that  we  have 
departed  from  Nature's  models  because  on  the  one 
hand  we  cannot  copy  her  ways  successfully,  and  on  the 
other,  within  certain  limitations,  we  are  able  to  produce 

336 


The  Conquest  of  the  Air 

things  of  our  own  which  answer  the  purpose  as  well  or 
even  better.  The  aeroplane  will  never  be  able  to  glide 
about  in  all  weathers  with  the  skill  and  certainty  of  the 
seagull,  but  for  a  plain,  straightforward  fly  it  may  soon 
be  able  to  rival  the  best  of  the  feathered  world. 

The  idea  of  imitating  the  bird,  indeed,  may  have  been 
the  means  of  delaying  the  day  of  ultimate  success,  by 
diverting  men's  minds  into  wrong  channels,  since  the 
boy's  kite,  a  simple  appliance  which  man  has  been 
making  for  centuries,  is  the  real  model  from  which  the 
flying-machine  has  grown. 

For  it  needs  to  be  made  quite  clear  that  there  is  no 
mysterious  secret  which  had  to  be  solved  before  men 
could  fly.  A  kite  is  an  aeroplane,  and  an  aeroplane,  in 
the  conventional  sense  of  the  word,  is  nothing  more 
than  a  self-propelled  kite. 

Every  boy  knows  that  there  are  two  ways  in  which 
a  kite  can  be  got  to  rise  in  the  air.  One  is  to  hold  it 
by  the  string,  while  the  wind  blows  under  its  inclined 
surface,  and  driving  as  it  were  a  huge  wedge  under  it, 
lifts  it  up.  The  second  method  is  used  if  there  is  not 
sufficient  wind  to  lift  the  kite.  The  same  result  can 
then  be  achieved  by  running  swiftly  along,  and  pulling 
the  kite  by  means  of  the  string  against  the  still  air. 
The  principle  is  precisely  the  same  in  both  cases,  namely, 
a  relative  movement  of  air  and  kite  against  each  other. 

Now  supposing  that,  instead  of  pulling  the  kite  along 
against  the  air  by  a  string,  we  could  furnish  it  with  a 
motor  and  a  screw-propeller,  by  which  it  could  drive 
itself  along,  the  result  would  obviously  be  just  the  same. 
There  we  have  the  idea  underlying  the  flying-machines  of 
to-day. 

The  theory  of  the  action  of  these  machines  can  be 
explained  thus.  When  we  walk  upstairs  we  place  first 
one  foot  and  then  the  other  upon  successive  stairs,  and 
press  downwards.  As  we  press  a  foot  downwards  upon 

337  Y 


The  Conquest  of  the  Air 

a  stair,  the  latter  reacts,  that  is,  exerts  an  upward 
pressure,  passive  it  is  true,  but  very  real  nevertheless, 
and  we  may  say  that  it  is  that  reaction  of  the  stairs 
which  enables  us  to  ascend.  We  can  see  this  from  an 
experience  which  most  of  us  have  gone  through  at  some 
time  or  other.  Who  has  not,  perhaps  in  the  dark  or  in 
a  fit  of  abstraction,  reached  the  top  of  a  flight  of  stairs, 
and  then  in  mistake  taken  another  upward  step.  The 
foot,  meeting  with  no  reaction  from  a  stair,  has  fallen 
swiftly,  and  caused  a  stumble,  startling  if  not  serious. 
In  that  false  step  we  made  just  the  same  action,  and 
exerted  just  the  same  force,  as  we  did  in  the  true 
steps  which  preceded  it,  but  we  did  not  raise  ourselves 


FIG.  46. — End  views  of  different  kinds  of  "  Planes."     If  either  of  these  be 
moved  swiftly  in  the  direction  of  the  arrows  it  will  tend  to  rise. 


any  higher.  In  other  words,  it  is  the  reaction  which 
raises  us. 

Now  let  us  apply  that  principle  to  the  kite  or  aero- 
plane. We  take  a  flat  or  approximately  flat  surface 
and  move  it  quickly  through  the  air,  holding  it  in  such 
a  position  meanwhile,  that  it  tends  to  throw  the  air 
downwards.  The  air  possesses  that  curious  property 
(inertia)  common  to  all  matter,  whereby  when  it  is  still 
it  likes  to  remain  still,  and  when  it  is  in  motion  it  resists 
any  stoppage  or  change  in  that  motion.  Therefore, 
when  the  movement  of  the  plane  tends  to  throw  the  air 
downwards,  the  air  resists  it  ;  in  other  words,  it  reacts 
upwards,  just  as  the  stair  reacts  against  the  pressure  of 
the  foot. 

We  see  the  same  thing  when  a  man  throws  a  cricket- 

338 


The  Conquest  of  the  Air 

ball.  The  ball  (and  his  arm  as  well),  owing  to  their 
inertia,  resist  the  sudden  forward  movement  which  con- 
stitutes the  throw,  and  therefore  react  backwards. 
For  this  reason  he  instinctively  places  one  foot  farther 
back  than  the  other,  when  throwing,  in  order  to  form 
a  sort  of  prop  to  resist  this  reaction.  It  is  possible, 
by  a  stretch  of  imagination,  to  think  of  a  man  raising 
himself  in  the  air  by  quickly  throwing  downwards  a 
succession  of  cricket-balls. 

The  difficulty  in  realising  this  reaction  of  the  air 
arises  from  the  fact  that  we  are  apt  to  regard  air  as 
being  infinitely  soft  and  "  giving."  Yet  we  know  that 
when  the  wind  blows  we  feel  its  force,  and  if  we  put  our 
heads  out  of  a  railway  carriage  window  we  feel  the 
resistance  which  even  still  air  is  able  to  offer  to  the 
passage  of  a  body  through  it.  These  facts  both  show 
that  air,  soft  and  yielding  though  it  may  be,  still  has 
some  of  the  properties  which  we  are  apt  to  associate 
with  solids,  though  in  a  slight  degree  only.  Indeed,  we 
may  put  it  that  air  has  a  certain  amount  of  "  solidity," 
due,  however,  not  to  the  adhesion  of  its  particles,  as  in 
a  true  solid,  but  to  the  inertia  of  each  separate  particle. 

Of  course  it  is  not  the  solidity  of  a  staircase.  If  we 
stop  for  a  moment  in  our  ascent  of  a  flight  of  stairs  we 
only  need  to  suspend  our  muscular  efforts,  but  if  we 
wish  to  remain  at  a  certain  height  in  a  flying-machine 
it  will  not  do  to  place  our  planes  so  that  they  cease  to 
throw  the  air  downwards,  for  the  bank  of  air  upon 
which  we  are  supported  is  too  soft,  and  we  should  sink 
in.  Therefore,  even  to  stay  at  a  uniform  level,  we  need 
to  have  our  planes  so  set  as  to  deflect  the  air  down- 
wards sufficiently  to  compensate  for  the  "  giving  way  " 
of  the  air  beneath  us. 

This  brief  explanation  of  the  principles  and  theory  of 
flight  in  a  machine  heavier  than  air  naturally  brings  us 
to  the  details  of  the  machines  themselves. 

339 


The  Conquest  of  the  Air 

In  this  connection  it  is  worthy  of  remark  that,  short 
though  the  time  is  since  the  flying-machine  has  been  a 
real  success,  it  has  been  sufficiently  long  for  certain 
definite  types  to  have  come  into  existence.  I  recently 
attended  an  international  exhibition  of  flying-machines, 
having  attended  the  similar  one  just  a  year  before,  and 
nothing  was  more  striking  than  the  obvious  fact  that  in 
the  course  of  that  year  there  had  been  no  change  at  all 
worth  mentioning  in  the  main  features  of  the  machines. 
Of  course  details  of  a  minor  nature  had  been  improved 
materially,  but  the  main  features  were  identically  the 
same. 

Nearly  all  machines  fall  into  the  two  classes  of 
monoplanes  and  biplanes.  As  the  words  indicate,  the 
former  has  one  plane  or  surface,  while  the  latter  has  two 
of  them. 

The  monoplane,  as  has  been  said,  is  in  its  main  out- 
lines like  a  bird  with  its  wings  outstretched.  There  is 
nothing  in  the  nature  of  a  flapping  action,  however,  the 
lifting  power  being  obtained  simply  by  the  curve  or 
inclination  of  the  plane  (or  pair  of  wings,  whichever 
we  like  to  call  it)  as  the  machine  is  driven  forward. 
The  driving  force  is  a  petrol  motor  similar  in  many 
cases  to  those  used  for  propelling  motor-cars,  except 
that  the  weight  is  "  skinned  down,"  that  is,  every  part  is 
reduced  to  the  lightest  possible  form  that  the  makers 
dare  to  adopt,  so  as  to  get  the  maximum  of  horse-power 
with  the  minimum  of  weight.  The  extent  to  which 
this  has  been  carried  will  be  understood  from  the  fact 
that  one  type  of  aeroplane  motor  gives  100  horse-power 
and  weighs  only  220  Ibs.,  so  that  the  weight  is  less  than 
2^  Ibs.  per  horse-power.  The  power  of  a  good  strong 
horse  from  only  that  small  weight  of  machinery  is  very 
striking. 

The  wings  are  generally  made  of  a  framework  of  either 
wood  or  light  metal  tubes,  braced  together  with  struts 

340 


The  Conquest  of  the  Air 

of  like  material  and  stays  of  fine  steel  wire.  Then  this 
framework  is  covered  with  a  special  fabric  something 
the  nature  of  "  mackintosh." 

The    backbone    of    the    monoplane,    or    part  which 
corresponds  to  the  body  of  a  bird,  is  also  made  of  a 


D 


As  seen  from  above. 


As  seen  from  one  side. 

FIG.  47.— Diagrams  showing  the  parts  of  a  Monoplane.  A.  Main  planes. 
B.  Body  or  backbone.  C.  Fins.  D.  Rudders.  E.  Balancing  planes. 
F.  Propeller.  M.  Motor. 

light  framework,  usually  covered  in  with  fabric  in  order 
to  give  some  protection  to  the  rider,  who  finds  his  seat 
within  this  framework  near  where  the  two  halves  of  the 
main  plane  (or  the  two  wings,  if  we  like  to  call  them  so) 
are  connected  to  it.  The  motor  is  also  placed  near  the 

341 


The  Conquest  of  the  Air 

same  position,  while  the  propeller  is  in  some  cases  at  the 
front  and  in  some  cases  behind. 

At  the  rear  end  of  the  backbone  or  body  there  is  a 
smaller  plane  or  pair  of  wings,  the  purpose  of  which  is 
to  control  the  "  tilt  "  or  angle  of  the  main  planes,  or  it 
may  be  described  as  a  sort  of  horizontal  rudder  by  which 
the  machine  can  be  steered  upwards  and  downwards. 
There  is  also  at  the  end  of  the  body,  or  in  the  tail  as  we 
might  term  it,  a  vertical  rudder  like  that  of  a  ship,  by 
which  the  machine  can  be  steered  to  either  side.  All 
these  are  controlled  by  means  of  wires  from  the  rider's 
seat. 

A  biplane  is  something  like  two  monoplanes  placed 
one  on  the  top  of  the  other.  Just  now  the  aeroplane 
was  referred  to  as  an  elaboration  of  the  kite,  and  just 
as  the  ordinary  flat  kite  is  a  monoplane,  so  the  box 
kite  is  a  biplane. 

Just  imagine  two  flat  surfaces  consisting  of  water- 
proof fabric  stretched  upon  a  frame  about  6  or  7  feet 
from  back  to  front  and  perhaps  40  feet  from  end  to 
end,  one  forming  a  kind  of  floor  with  another  one  like 
a  low  roof  over  it,  supported  upon  light  wooden  or 
tubular  uprights,  with  diagonal  ties  of  fine  wire  to  keep 
the  whole  affair  from  collapsing  sideways,  and  there 
you  will  have  a  good  representation  of  the  main  planes 
of  a  biplane. 

The  rider  sits  on  a  seat  at  the  centre  of  the  lower 
plane  with  the  motor  just  behind  him.  Stretching 
backwards  behind  the  motor  there  is  usually  a  long 
framework  which  carries  at  its  end  small  planes,  to 
prevent  the  machine  from  tipping  over  forwards  or 
backwards,  and  a  rudder  for  steering  to  either  side.  In 
some  cases  the  rear  planes  are  movable,  so  as  to  form 
horizontal  rudders  as  described  in  the  monoplane,  but 
in  some  makes  they  are  fixed,  while  there  is  a  hori- 
zontal rudder,  or  elevating  plane  as  it  is  termed,  at 

342 


The  Conquest  of  the  Air 

the  end  of  a  short  light  framing  in  front  of  the  main 
planes. 

Some  of  these  machines  have  two  propellers  side  by 
side  and  some  have  only  one.  In  the  former  case 
they  are  driven  by  means  of  chains  as  the  rear  wheel 
of  a  bicycle  is  driven,  but  in  the  latter  the  propeller  is 
generally  connected  directly  to  the  shaft  of  the  engine. 

The  propellers  are  mostly  made  of  wood,  and  gene- 
rally they  have  only  two  blades. 

These  machines  are  to  a  certain  extent  self-balancing, 
but  nearly  all  flying-machines,  whether  biplanes  or 


B 


FIG.  48.— Side  view  of  a  Biplane.     A.  Main  planes.     B.  Elevating  planes. 
C.  Rear  planes.     D.  Rudder.     K.  Balancing  planes. 

monoplanes,  are  balanced  by  the  action  of  the  rider 
himself  in  one  of  two  ways.  One  is  to  pull  the  planes 
out  of  shape  a  little  by  means  of  wires  led  to  the 
driver's  seat.  Thus  if  he  feels  himself  tilting  over  to  the 
right,  for  example,  he  manipulates  these  wires  so  that 
the  right-hand  end  is  twisted  upwards  and  the  left-hand 
downwards.  The  right-hand  end  then  tries  to  steer  its 
way  upwards  and  the  left-hand  end  the  opposite  way, 
and  so  the  balance  is  restored.  The  wires  are  worked 
by  a  single  handle,  the  movement  of  which  in  one 
direction  raises  the  right-hand  end  of  the  machine  and 
the  other  the  left. 

The   second   method   is   by  means   of  small  planes 
hinged  to  the  back  edges  of  the  larger  planes.     These 

343 


The   Conquest  of  the  Air 

are  called  balancing  planes,  and  are  in  fact  horizontal 
rudders  by  means  of  which  one  side  of  the  machine 
can  be  steered  upwards  while  the  other  is  steered 
downwards.  The  man,  after  a  little  practice,  becomes 
so  used  to  working  his  balancing  planes,  that  he 
balances  his  machine  as  instinctively  as  a  bicyclist  does, 
without  any  thought  or  conscious  effort.  By  this  means 
a  much  greater  degree  of  stability  can  be  assured  than 
seems  possible  by  any  method  of  automatic  balancing, 
for  so  long  as  he  keeps  his  presence  of  mind  he  can 
recover  his  balance  even  after  he  has  been  tilted  to  a 
considerable  angle  by  a  sudden  gust  of  wind.  It  is 
easy  to  see  that  this  is  a  matter  of  the  greatest  import- 
ance to  the  utility  of  the  flying-machine,  for  if  it  is  only 
going  to  be  a  fair-weather  craft,  and  incapable  of  taking 
care  of  itself  in  moderately  bad  weather,  its  sphere  of 
usefulness  is  seriously  curtailed.  There  seems  every 
reason  to  believe,  however,  that  the  difficulty  of  bad 
weather  is  quickly  being  overcome,  and  that  just  as  the 
bicycle,  which  used  to  be  a  fair-weather  machine,  to  be 
left  at  home  when  the  roads  were  bad  or  greasy,  has 
now  become  useful  and  reliable  under  all  circumstances, 
so  the  aeroplane  will  soon  be  able  to  veature  out  under 
almost  any  conditions. 

There  are  a  few  machines  made  of  the  "  triplane  " 
variety,  in  which  another  plane  is  placed  above  the 
others,  but  up  to  the  present  these  have  not  been 
largely  used. 

There  is  a  general  idea  that  it  is  very  dangerous  to 
venture  high  up  in  one  of  these  machines,  but  that  is 
not  necessarily  the  case.  Indeed,  other  circumstances 
being  the  same,  a  man  is  almost  safer  the  higher  he 
goes.  This  strange  circumstance  is  due  to  the  fact 
that  one  of  the  most  fruitful  sources  of  failure  at  present 
is  the  motor.  Even  motor-cars  are  sometimes  to  be 
seen  stopped,  through  the  failure  of  the  motor,  by  the 

344 


The  Conquest  of  the  Air 

roadside,  and  when  we  remember  the  lightness  of  the 
aeroplane  motors,  it  is  not  to  be  wondered  at,  if  they 
should  be  even  more  liable  to  break  down  than  their 
stouter  brothers  of  the  road.  Now  if  the  engine  of  an 
aeroplane  stops,  there  is  little  or  no  danger  so  long  as 
there  is  a  suitable  open  spot  within  reach  upon  which 
to  land,1  and  if  the  machine  is  high  up  in  the  air,  it  can 
travel  for  quite  a  long  distance  without  the  engine's 
assistance,  though  of  course  it  is  gradually  descending 
all  the  time.  Thus  when  high  up  the  rider  has  a  very 
fair  chance  of  looking  round  him  and  finding  a  suitable 
landing-place,  whereas,  if  near  the  ground  he  has  no 
such  opportunity,  but  must  come  to  earth  at  once,  even 
if  he  has  to  alight  among  a  neighbour's  chimney-pots. 
Moreover,  at  high  altitudes  the  movements  of  the  air  are 
free  from  the  gusts  and  eddies  caused  by  contact  with 
obstructions  such  as  trees,  buildings,  and  hills. 

On  the  other  hand,  there  is  little  safety  in  being  near 
the  ground,  for  a  fall  of  say  20  feet  is  quite  likely  to  be 
fatal,  and  one  from  1000  feet  can  be  no  worse  than 
that. 

The  most  serious  danger  to  the  aeronaut  is  the 
failure  of  the  actual  machine  itself.  If  some  part  gives 
way  and  throws  the  machine  out  of  balance,  say  the 
collapse  of  one  end  of  the  main  plane,  nothing  whatever 
can  save  a  terrible  disaster.  This  danger  can  only  be 
provided  against  by  the  most  careful  attention  to  every 
detail  of  the  construction  of  the  machine. 

Though  not,  strictly  speaking,  connected  with  the 
conquest  of  the  air,  a  short  reference  may  perhaps  be 
made  here  to  those  curious  water  craft  known  as 
"  hydroplanes,"  since  they  proceed  upon  the  surface 
of  the  water  on  precisely  the  same  principle  as  the 

1  I  have  actually  seen  M.  Paulhan,  the  hero  of  the  first  long-distance  cross- 
country flight  in  England,  stop  his  engine  when  some  600  feet  up  and  come 
to  the  ground  as  gently  as  a  seagull  alights  upon  the  water. 

345 


The  Conquest  of  the  Air 

aeroplane  may  be  said  to  glide  upon  the  surface  of  a 
bank  of  air.  When  still  or  travelling  slowly,  they  float 
in  the  water  just  as  an  ordinary  boat  does,  but,  as  soon 
as  they  are  driven  to  a  certain  speed,  they  rise  upon  the 
surface  of  the  water  and  skim  over  it  with  remarkable 
swiftness.  This  they  are  able  to  do  because  of  the 
peculiar  shape  of  the  hull,  the  bottom  of  which  forms 
a  flat  plane  capable  of  acting  upon  the  water  just  as  the 
planes  of  a  flying  machine  act  upon  air.  One  of  these 
curious  craft  is  shown  in  the  upper  illustration  facing 
this  page,  while  underneath  it  is  a  similar  boat,  invented 
by  Sir  John  Thornycroft,  the  famous  builder  of  fast 
warships,  which  combines  the  skimming  powers  of  the 
hydroplane  with  more  seaworthy  properties  than  such 
craft  usually  possess. 

The  hydroplane  skimming  across  the  surface  of  the 
water,  as  a  flat  stone  can  be  made  to  do  if  skilfully 
thrown,  affords  another  illustration,  which  may  appeal 
specially  to  some  readers,  of  the  principle  underlying 
both  hydroplanes  and  aeroplanes.  The  difference,  too, 
between  the  stone  heavier  than  water  yet  supported 
upon  its  surface  because  of  its  shape  and  speed,  and 
a  log  of  wood  which  is  supported  in  the  water  because 
of  its  being  lighter  than  water,  illustrates  the  difference 
between  the  two  kinds  of  aerial  craft. 

Those  which  we  have  been  considering  are  heavier 
than  air,  and  owe  their  ability  to  stay  supported  upon 
it  to  their  shape  and  movement.  We  will  now  take  a 
look  at  those  which  are  lighter  than  air,  and  float 
because  of  their  lightness. 

Of  course,  the  ordinary  spherical  balloon  has  been 
known  for  many  years.  It  consists  of  a  gas  bag  or 
envelope  of  some  light  but  gas-proof  material,  to  which 
is  suspended  a  car  capable  of  holding  a  few  people. 
In  order  to  provide  a  means  of  attaching  the  car  to  the 
flimsy  material  of  which  the  balloon  is  made,  the 

346 


A  "HYDROPLANE" 

This  craft  glides  upon  the  surface  of  water  as  an  aeroplane  glides  upon  air. 


By  permission  of 


Messrs.  J.  I.  Thornycroft  &•  Co.,  Ltd. 


A  "SKIMMER" 


Invented  by  Sir  John  Thornycroft,  which  at  low  speeds  floats  just  like  an  ordinary 
boat,  but  which  when  driven  at  about  twenty  knots  rises  up  on  to  the  surface  and  skims 
along  like  a  hydroplane,  its  speed  then  increasing  to  twenty-seven  knots  (over  thirty 
miles)  an  hour. 


The  Conquest  of  the  Air 

envelope  is  generally  enclosed  in  a  large  bag  of  net- 
work, to  which  the  car  is  actually  suspended. 

The  buoyancy  of  the  balloon  is  due  to  its  being  filled 
with  a  gas  lighter  than  air,  until  it  is  so  distended  that 
it  takes  up  more  space  than  does  an  equal  weight  of 
air.  Then  it  floats  for  precisely  the  same  reason  that 
a  ship  floats  in  water.  The  ascent  and  descent  of  a 
balloon  is  arranged  by  very  simple  means.  Around 
the  car  there  are  tied  bags  of  sand,  and  if  the  aeronaut 
wishes  to  go  higher,  he  simply  lets  fall  some  of  the 
sand  from  these  bags.  That  lightens  the  balloon,  and 
it  ascends.  The  descent  is  controlled  by  means  of  a 
valve  in  the  top  of  the  balloon  by  which  gas  can  be 
permitted  to  escape,  and  so  the  balloon  be  allowed  to 
become  slightly  deflated.  This  valve  is  worked  by  a 
cord  from  the  car,  and  when  the  balloon  is  wanted  to 
descend  the  discharge  of  a  little  gas  will  cause  it  to 
do  so. 

Thus,  as  long  as  there  is  ballast  left  in  the  car  and 
sufficient  gas  in  the  envelope,  the  ascent  and  descent 
can  be  controlled. 

For  suddenly  deflating  the  balloon  in  the  act  of 
alighting  upon  the  earth  there  is  a  "  ripping  panel," 
a  patch  lightly  sewn  on  the  envelope,  which  a  vigorous 
pull  upon  a  rope  will  tear  right  out,  and  so  let  all 
the  gas  escape  almost  instantaneously.  But  for  this, 
there  is  a  danger  of  the  wind  catching  the  balloon 
while  still  partially  inflated  and  dragging  it  along  the 
ground,  but  with  it  the  moment  the  car  touches  earth 
the  rope  can  be  pulled,  and  instantly  the  whole  thing 
collapses. 

The  gas  most  commonly  used  for  balloons  is  coal 
gas,  the  weight  of  which  is  such  that  1000  cubic  feet 
will  lift  40  Ibs.  More  effective  is  hydrogen,  which  will 
lift  about  twice  as  much,  but  it  is  too  expensive  except 
for  special  purposes. 

347 


The  Conquest  of  the  Air 

Hydrogen  for  use  in  balloons  can  be  obtained  by 
decomposing  steam  somewhat  in  the  manner  described 
in  an  earlier  chapter.  If  a  jet  of  steam  be  blown 
through  a  tube  containing  white-hot  pieces  of  iron, 
the  steam  is  split  up  into  oxygen  and  hydrogen,  the 
former  of  which  combines  with  the  iron  at  once  and 
leaves  the  hydrogen  free. 

An  ordinary  spherical  balloon  cannot  be  propelled 
or  steered,  for  it  simply  drifts  with  the  wind.  It  has 
been  put  that  such  a  balloon  is  in  a  perpetual  calm,  for, 
however  fast  it  is  moving,  the  surrounding  air  is  moving 
in  precisely  the  same  direction,  and  at  precisely  the 
same  speed.  A  ship  can  take  advantage  of  the  force 
of  the  wind  because  it  is  supported  in  the  water — in 
other  words,  it  is  the  difference  in  motion  between  the 
sea  and  the  air  which  enables  a  sailing-ship  to  propel 
and  steer  itself — but  the  balloon,  being  entirely  im- 
mersed in  air,  can  only  drift  with  the  air,  unless  it 
has  some  powerful  mechanical  force  to  assist  it.  The 
force  generally  used  is  a  petrol  motor,  driving  a  pro- 
peller ;  and  in  order  that  it  may  cleave  its  way  through 
the  air  with  the  least  possible  resistance,  steerable 
balloons  are  made  of  elongated  shape  with  pointed 
or  rounded  ends. 

There  are  two  types  of  these  airships,  known  as 
rigid  and  non-rigid  respectively.  The  former  are  kept 
in  shape  by  means  of  a  rigid  framework,  while  the 
latter  owe  their  form  to  the  gas  bag  being  fully  dis- 
tended with  gas. 

Most  unlikely-looking  materials  are  sometimes  used 
for  these  balloons,  some  of  them  being  made  of  metal, 
and  not  always  of  the  lightest  metal  available — alu- 
minium— but  even  of  iron.  Structures  of  such  weight 
are  necessarily  of  enormous  size  or  they  could  not 
possess  sufficient  buoyancy.  For  example,  one  has 
recently  taken  the  air  which  is  120  metres  long,  and 

348 


The  Conquest  of  the  Air 

holds   13,000  cubic   metres  of    gas — close   on    half    a 
million   cubic  feet. 

This  particular  airship  has  four  petrol  motors,  aggre- 
gating 250  horse-power. 

Wonderful  structures  these  are,  but  there  seems  to 
be  reason  to  doubt  whether  they  will  ever  be  able  to 
overcome  the  one  inherent  obstacle  to  success,  namely, 
their  huge  size  and  the  consequently  great  resistance 
which  they  offer  to  the  air.  It  is  inconceivable  that 
they  will  ever  be  able  to  proceed  against  a  strong  wind  ; 
and  when  at  anchor,  fastened  to  the  ground,  a  very 
moderate  gust  is  sufficient  to  wreck  them. 

Attempts  have  been  made  to  combine  the  two  types 
of  flying  machine,  a  notable  example  of  which  is  a 
huge  steerable  balloon  of  the  rigid  type,  nearly  200 
feet  long  and  33  feet  in  diameter,  which  for  its  car  has 
a  monoplane  which  can  be  detached  if  and  when 
desired.  This  balloon  is  interesting,  too,  in  that  it  is 
stiffened  by  an  ingenious  arrangement  of  rubber  tubes, 
which  are  made  rigid  by  being  filled  with  compressed 
air. 

In  concluding  this  chapter,  I  must  give  a  brief 
reference  to  a  remarkable  motor  which  has  been  devised 
specially  for  aerial  craft,  and  which  is  very  largely  used. 
It  is  called  the  "  Gnome  "  engine,  and  has  already  been 
referred  to  because  of  its  remarkable  lightness. 

The  cylinders  are  arranged  like  the  spokes  of  a 
wheel  around  a  central  hub,  which  forms  the  crank 
chamber.  Unlike  all  other  engines  in  which  the 
cylinders  are  still  while  the  crank  is  turned,  the  crank 
in  this  case  remains  still  and  the  cylinders  revolve 
themselves  round  it.  Thus  the  engine  forms  its  own 
fly-wheel,  and  moreover  the  cooling  of  the  cylinders,  an 
important  thing  in  all  internal-combustion  engines,  is 
accomplished  automatically  by  their  swift  and  con- 
tinual motion  through  the  air. 

349 


CHAPTER    XXVII 
A  MISCELLANEOUS   CHAPTER 

THERE  are  a  number  of  interesting  examples  of  the 
engineer's  skill  which  do  not  naturally  fall  under  any 
of  the  headings  of  the  preceding  chapters,  and  so  I 
propose  to  gather  a  few  of  the  most  striking  of  them 
here. 

The  motor-car  branch  of  engineering  has  not  been 
referred  to  at  length,  because  there  is  quite  a  large 
range  of  popular  books  on  the  subject,  and  many 
people  are  familiar  with  it  who  are  quite  outside  the 
engineering  profession.  There  are,  however,  one  or 
two  special  features  which  deserve  a  reference.  One 
of  these  is  the  Renard  train. 

This  consists  of  a  train  of  vehicles  hauled  by  a  motor 
wagon  much  as  a  locomotive  hauls  a  railway  train, 
only  it  is  for  use  on  ordinary  roads.  In  the  ordinary 
way,  if  a  trailer  be  attached  to  some  form  of  road 
locomotive,  it  can  be  steered  quite  satisfactorily,  but  if 
many  were  so  attached  there  would  be  trouble  in  going 
round  corners,  for  each  one  would  take  a  different 
curve  from  the  one  in  front,  until  they  would  be 
colliding  with  the  building  at  the  corner.  A  certain 
officer  in  the  French  army,  however,  saw  the  utility, 
for  military  purposes  particularly,  of  being  able  to  haul 
a  long  train  of  wagons  in  this  way,  so  he  devised  a 
means  of  getting  over  this  difficulty.  The  locomotive 
not  only  propels  itself,  but  propels  every  vehicle  on  the 
train  as  well.  It  does  not  simply  pull  it  along  but 

350 


A  Miscellaneous  Chapter 

drives  it  by  turning  its  wheels,  or  holds  it  back  when 
necessary  by  restraining  the  rotation  of  the  wheels. 
The  whole  train  is  coupled  together  by  special  coup- 
lings so  that  it  is  as  if  there  were  a  continuous  shaft 
running  the  whole  length,  the  turning  of  which  turns 
all  the  wheels,  yet  it  is  flexible  between  the  vehicles,  so 
that  the  train  can  easily  go  round  corners.  And  not 
only  does  the  "  engine "  do  that.  There  is  a  special 
steering  coupling  as  well,  which  causes  each  vehicle  to 
steer  the  one  behind  it  in  exactly  the  same  course 
which  it  takes  itself.  Thus,  wherever  the  "  engine  " 
goes  the  trailing  wagons  follow  exactly  ;  if  it  quickens 
its  pace  they  do  the  same,  or  if  it  slows  down  they  slow 
down  too.  Such  a  train  can  consequently  go  almost 
anywhere,  through  narrow,  crooked  streets  or  over 
rough  ground.  It  can  turn  the  sharpest  corners,  and 
each  succeeding  vehicle  will  follow  the  preceding  one 
just  as  if  they  were  running  on  rails  ;  indeed  it  can 
curl  itself  up  into  a  spiral  just  as  easily  as  it  can  go 
along  a  straight  road  ;  and  it  can  go  backwards  just  as 
easily  as  forwards. 

Another  very  interesting  motor  vehicle  is  the  motor 
sleigh  made  for  Captain  Scott's  Antarctic  expedition. 
This  has  four  wheels,  two  on  each  side,  just  like  a 
motor-car,  except  that  instead  of  being  ordinary  road 
wheels  they  are  tooth  wheels,  and  round  the  pair  on 
each  side  there  is  an  endless  chain  something  like  that 
on  a  bicycle,  only  larger.  Moreover,  it  has  large  teeth 
on  its  under  side,  so  that  it  can  grip  the  snow.  The 
weight  of  the  sleigh  rests  upon  these  chains,  so  that 
when  the  motor  turns  the  wheels  and  moves  the  chain 
round  and  round,  the  chain  gripping  the  snow  by 
means  of  its  teeth,  no  matter  how  smooth  it  may  be, 
propels  the  sleigh  along.  It  does  not  travel  fast,  being 
designed  for  two  to  three  miles  per  hour,  but  it  is 
capable  of  pulling  several  ordinary  sleighs  behind  it. 

351 


A  Miscellaneous  Chapter 

To  go  to  another  department  altogether,  many 
readers  will  probably  be  interested  to  know  something 
about  freezing  machinery.  This  is  a  most  important 
branch  of  engineering,  since  without  it  many  parts  of 
the  world  would  find  a  large  part  of  their  food-supply 
cut  off.  The  method  by  which  extreme  cold  can  be 
produced  mechanically  was  explained  in  an  earlier 
chapter  in  connection  with  the  production  of  oxygen 
for  engineering  purposes.  The  same  principle  is  em- 
ployed in  a  refrigerating  machine  on  board  ship  or  in  a 
cold  storage. 

Some  compressible  gas,  such  as  carbonic  acid,  is  first 
compressed  by  a  pump.  Then  it  is  passed  through 
pipes  with  water  circulating  outside  them,  like  a  surface 
condenser.  This  has  the  effect  of  cooling  the  com- 
pressed gas,  so  that  when  it  reaches  the  refrigerator 
proper,  in  which  it  is  allowed  to  expand,  it  falls  to  a 
very  low  temperature.  The  cold  thus  produced  is 
carried  into  the  chamber  which  is  to  be  cooled  either 
by  blowing  air  through  the  refrigerator  into  the 
chamber  or  else  by  a  non-freezable  liquid  circulating 
through  the  refrigerator  and  then  around  pipes  in  the 
chamber,  just  as  heat  is  often  conveyed  from  a  boiler 
into  a  public  building,  only  in  this  case,  of  course,  it  is 
cold  which  is  conveyed,  and  not  heat. 

Some  remarkable  machines  are  to  be  found  in  con- 
nection with  printing.  The  large  rotary  printing 
machines  which  turn  out  newspapers  by  the  mile  are 
too  complicated  in  their  details  to  be  described  min- 
utely here,  but  it  will  be  sufficient  to  say  that  there  is 
a  large  cylinder  which  rotates  about  a  horizontal  axis. 
On  this  is  fixed  the  type,  or  rather  a  plate  which  has 
been  cast  off  the  type  so  that  it  forms  a  perfect  replica  of 
it.  This  is  bent  round  and  securely  attached  to  the 
cylinder,  and  then  the  latter  rotates  at  a  high  speed,  the 
paper  (which  is  like  a  huge  ribbon  on  a  reel)  running 

352 


A  Miscellaneous  Chapter 

under  it.  As  soon  as  the  impression  has  been  made 
on  one  side,  the  paper  passes  another  cylinder  which 
prints  the  other  side,  and  then  a  knife  cuts  the  paper 
the  correct  size  and  in  the  right  place.  Finally  it  folds 
the  paper,  and,  in  some  cases  where  there  is  more  than 
one  sheet,  gums  the  inside  one.  Thus  the  machine 
takes  in  a  roll  of  paper  and  turns  out  newspapers 
printed,  cut,  folded,  gummed,  and  counted. 

The  marvels  of  the  rotary  printing  machine  are, 
however,  quite  put  in  the  shade  by  some  of  the  type- 
setting machines,  the  action  of  which  is  almost 
human.  The  one  used  for  newspapers  is  called  the 
"  linotype,"  and,  as  its  name  implies,  it  makes  a  line  of 
type  at  a  time — one  solid  type,  that  is,  for  each  line,  and 
not  separate  type  for  each  letter.  This  has  the  draw- 
back for  other  than  newspaper  work  that,  if  a  word 
has  to  be  altered,  it  is  not  easy  to  do  it ;  but  in  another 
and  perhaps  more  wonderful  machine  still,  the  "  mono- 
type," a  separate  type  is  made  for  each  letter,  and  so 
alterations  can  be  made  as  easily  as  with  hand-set 
type. 

This  marvellous  machine,  which  is  often  used  for 
books,  consists  of  two  parts,  the  key-board  and  the 
caster. 

The  former  is  very  like  the  keyboard  of  a  typewriter, 
except  that  it  has  a  very  large  number  of  keys.  The 
operator  sits  at  his  machine  and  writes  out  his  matter 
just  as  a  typist  would,  the  result  being,  however, 
simply  to  punch  a  lot  of  little  holes  in  a  long  strip  of 
paper. 

Now  every  one  must  have  noticed  that  there  is  a  very 
important  difference  between  typewriting  and  printing. 
In  the  latter  case  the  lines  are  all  exactly  the  right 
length,  but  in  the  former  they  vary.  In  hand-setting 
the  compositor  adjusts  each  line — or  justifies,  as  he  calls 
it — by  putting  in  thicker  or  thinner  spaces  between  the 

353  z  * 


A   Miscellaneous  Chapter 

words  so  as  to  make  them  fill  out  the  line  precisely.  But 
how,  one  is  tempted  to  ask,  can  that  possibly  be  done  by 
machine  ;  for,  as  in  the  case  of  the  typewriter,  when  you 
depress  the  space-key  to  make  a  space,  you  do  not  know 
how  the  line  is  going  to  turn  out  as  regards  length. 

In  the  monotype  this  difficulty  is  got  over,  as  we 
shall  see,  in  a  very  simple  and  effective  way.  When 
the  end  of  the  line  is  near,  and  the  operator  finds  that 
he  cannot  get  another  word  in,  he  presses  a  key  and 
instantly  a  little  indicator  shows  him  what  size  of 
space  he  will  need  to  have  between  the  words  to  make 
the  line  exactly  the  right  length.  Then  he  presses 
suitable  keys,  which  record  that  size  by  means  of  holes 
in  the  paper.  Now  that  paper,  as  we  shall  see  presently, 
goes  at  a  later  stage  to  the  caster,  which  makes  the  type 
in  accordance  with  the  holes  in  it,  and  it  is  important 
to  note  that  it  starts  at  the  end  of  the  line  and  sets  it 
up  backwards.  When,  in  punching  the  strip  by  means 
of  the  keyboard,  the  operator  comes  to  the  end  of  a 
word,  he  presses  a  "  space  "  key  just  as  a  typist  does. 
This  makes  holes  indicating,  as  we  might  put  it,  "  a 
space  is  to  come  here,"  but  it  does  not  show  the  width 
of  that  space.  When  he  gets  to  the  end  of  the  line,  as 
we  have  seen,  he  presses  a  special  key  and  that  makes 
holes  indicating  "  the  spaces  in  this  line  need  to  be  of 
such  and  such  a  thickness." 

Thus  when  the  caster  begins  a  line,  since  it  works 
backwards,  the  first  indication  it  finds  on  the  strip  is  the 
instructions  as  to  how  thick  the  spaces  need  to  be,  and 
after  that,  whenever  it  comes  across  the  instructions  to 
make  a  space,  it  makes  it  that  thickness.  By  this 
means  every  line  is  just  the  right  length. 

The  caster  is  quite  separate  from  the  keyboard,  in 
fact,  they  are  usually  in  separate  apartments,  for  the 
former  makes  considerable  noise  while  the  latter  is  best 
worked  under  quiet  conditions.  It  is  a  most  complicated 

354 


A  Miscellaneous  Chapter 

piece  of  mechanism,  but  its  mode  of  working  may  be 
described  briefly.  The  paper  strip  passes  over  a  plate 
with  a  row  of  holes  in  it,  and  under  an  indiarubber 
pad  with  a  hollow  in  its  surface,  into  which  compressed 
air  is  pumped.  Thus  as  soon  as  a  hole  in  the  paper 
comes  over  one  of  the  holes,  the  air  can  pass  into  the 
hole,  but  otherwise  the  holes  are  kept  closed  by  the 
paper.  The  compressed  air  passing  through  different 
combinations  of  holes  causes  different  movements  in 
a  little  frame  which  is  filled  with  brass  dies,  each  one 
having  cut  into  its  surface  the  impression  of  a  letter 
or  character  of  some  sort,  or  else  a  plain  block  to  form 
a  space. 

Underneath  this  frame  there  is  a  plate  with  a  little 
square  hole  in  it  of  variable  width,  and  as  soon  as  the 
holes  in  the  paper  uncover  the  holes  meaning  a  certain 
letter,  the  frame  moves  so  as  to  bring  that  particular 
die  over  the  hole  and  at  the  same  time  the  hole  opens 
or  closes  up,  as  the  case  may  be,  so  as  to  produce 
a  type  exactly  the  right  width  for  that  letter.  At  the 
same  moment  a  little  pump  sends  up  a  jet  of  liquid 
type-metal  into  the  hole,  completely  filling  it.  This 
sets  instantly,  and  then  a  knife  comes  along  and  cuts 
off  the  bottom  of  the  type  so  as  to  make  it  exactly  the 
right  height,  and  then  the  machine  pushes  out  the  finished 
type  on  to  a  little  table  set  to  receive  it.  As  soon  as 
one  line  is  finished  the  machine  itself  pushes  it  upwards 
and  so  leaves  room  for  the  next  line  to  take  its  place. 

Thus  any  one  watching  this  machine  at  work  sees  a 
constant  stream  of  newly  made  type  coming  out  in 
quick  succession,  one  line  succeeding  another  with 
surprising  rapidity. 


355 


CHAPTER  XXVIII 
ENGINEERING  OF  TO-MORROW 

IT  is  a  notoriously  dangerous  thing  to  prophesy,  but 
one  cannot  help  observing  certain  tendencies  which 
have  characterised  the  progress  of  the  recent  past,  and 
it  is  quite  reasonable  to  suppose  that  they  will  continue 
to  mould  the  progress  of  the  near  future.  From  them, 
therefore,  some  suggestion  as  to  future  developments 
can  be  obtained. 

It  will  be  mere  suggestion,  however,  for  there  can 
be  no  doubt  that  progress  will  be  increasingly  rapid, 
and  exactly  where  it  will  lead  us  to  is  impossible  to  tell. 
New  discoveries  in  science  will  probably  open  up  new 
opportunities  for  the  engineer,  just  as  modern  dis- 
coveries in  electricity  have  done.  But  of  one  thing  we 
may  be  quite  certain  ;  for  many  years  to  come  the 
energies  of  the  engineer  will  be  directed  largely  to  the 
utilisation  of  waste  materials  and  waste  forces. 

The  amount  of  force  that  is  being  wasted  now  is 
little  realised  outside  the  engineering  profession.  For 
example,  coal  contains  a  certain  measurable  amount  of 
energy  which  we  often  desire  to  convert,  for  conveni- 
ence of  transmission,  into  electrical  energy.  We  have 
the  most  elaborate  machinery  for  doing  this,  machinery 
on  which  we  pride  ourselves,  and  which  we  consider 
typifies  the  progress  of  the  present  day,  yet  how  much 
of  the  coal's  energy  do  we  lose  in  the  process  ?  In  an 
up-to-date  generating  station  not  much  more  than  ten 
per  cent,  of  the  energy  of  the  coal  consumed  passes 

356 


Engineering  of  To-morrow 

out  in  the  form  of  electrical  energy.  Nine-tenths  of 
it  are  lost. 

Let  us  consider  what  that  means.  Coal  is  a  com- 
modity of  which  there  is  but  a  limited  supply.  The 
supply  may,  it  is  true,  be  enough  for  another  century, 
but  there  must  be  an  end  to  it  ultimately.  In  Great 
Britain  alone,  for  example,  the  production  of  coal  runs 
into  well  over  250  million  tons  per  annum,  a  rate 
which  obviously  cannot  be  kept  up  for  an  unlimited 
period  ;  and  there  are  other  countries  which  are  equally 
prodigal. 

Now,  under  modern  conditions,  industry  largely, 
indeed  almost  entirely,  depends  upon  coal.  Where  the 
coal  is  there  will  the  industries  gather.  This  statement 
is  entirely  and  absolutely  true  except  for  those  few 
places  where  there  is  an  abundance  of  water-power  ; 
but,  as  such  places  are  comparatively  rare,  we  may 
almost  disregard  them  when  taking  a  general  survey 
of  the  situation. 

We  are  therefore  confronted  with  three  alternatives. 
First,  vast  supplies  of  coal  may  be  found  elsewhere,  in 
new  countries,  which  will  be  able  to  meet  the  needs  of 
the  world  for  many  centuries,  but  that  will  inevitably 
mean  that  the  industries  will  move  to  those  places 
where  the  coal  is  to  be  found ;  for  it  is  easier  and 
cheaper  to  take,  once  for  all,  the  factory  to  the  coal 
than  it  is  to  keep  on,  year  after  year,  continually 
bringing  the  coal  to  the  factory.  If  this  is  to  be  the 
ultimate  solution  of  the  problem,  then  it  must  mean  a 
terrible  dislocation  of  the  existing  arrangements  and  a 
serious  loss  to  existing  interests. 

Let  us  imagine  for  a  moment  what  would  happen  if 
the  coal  in  South  Wales  were  to  give  out,  while  more 
abundant  supplies  still,  and  equally  good,  were  found, 
say,  at  some  convenient  spot  on  the  coast  of  Africa. 
The  great  iron,  steel,  and  tinplate  mills  in  South  Wales 

357 


Engineering  of  To-morrow 

would  of  necessity  have  to  be  moved  to  the  neighbour- 
hood of  other  coalfields.  The  shops  which  supply 
the  needs  of  the  workers  in  these  mills  would  find 
their  trade  gone ;  businesses  which  had  been  built  up 
by  a  lifetime  of  care  and  industry  would  quickly  cease 
to  exist.  The  owners  of  property  would  suffer  equally, 
and  the  effect  of  this  general  decline,  even  of  one 
district  only,  would  react  in  other  places  and  cause 
widespread  misery. 

The  workers  themselves  could  probably  follow  the 
work  to  its  new  location,  but  even  that  would  mean 
the  breaking  up  of  many  families,  and  be  the  source 
of  much  personal  suffering. 

Yet  if  the  imagined  failure  of  the  supply  in  South 
Wales  were  made  up  by  a  new  supply  from  new 
sources,  the  world  as  a  whole  would  be  just  as  well  off 
as  before.  We  can  see,  therefore,  that  the  discovery 
of  new  coalfields  to  replace  the  old,  while  it  may  keep 
the  world  going  industrially,  will  be  accompanied  with 
serious  consequences  to  whole  communities  which  we 
ought  to  endeavour  to  stave  off  as  long  as  possible. 

The  second  alternative  is  the  discovery  of  some  new 
source  of  power  which  can  be  obtained  anywhere,  so 
that  it  can  be  used  by  existing  factories  without  neces- 
sitating their  removal  to  new  districts.  Now  there  is 
practically  only  one  source  of  all  energy,  the  heat  of 
the  sun.  As  has  been  pointed  out  already,  wind-power 
is  the  result  of  the  sun's  action,  and  so  is  water-power, 
while  the  energy  of  coal  is  entirely  due  to  the  action 
of  the  sun's  heat  in  times  gone  by. 

The  sun  itself,  astronomers  tell  us,  will  in  time  grow 
cold,  having  exhausted  its  vast  stores  of  energy,  but 
that  will  not  be,  they  reckon,  for  millions  of  years,  so 
for  the  moment  we  may  regard  the  sun  as  the  one 
permanent  element  in  the  situation.  Is  there  not  then 
the  possibility  that  we  may  find  some  more  effective 

358 


Engineering  of  To-morrow 

way  of  catching  and  turning  to  account  the  energy 
which  is  streaming  to  us  from  the  sun.  A  friend  of 
mine  has  a  theory,  a  pure  theory  at  present,  which 
may  contain  the  germ  of  some  such  solution  of  the 
problem.  He  says  the  earth  and  the  sun  remind  him 
of  a  dynamo.  This  machine,  as  we  know,  consists 
of  two  parts — an  armature  which  rotates,  and  a  field- 
magnet  which  provides  a  kind  of  bath  of  magnetism 
within  the  influence  of  which  the  rotation  takes  place, 
and  it  is  the  movement  of  the  armature  within  the 
influence  of  the  field-magnets  which  causes  the  current 
to  be  generated.  Now,  says  this  theory,  the  earth  is 
revolving  within  the  influence  of  something  analogous 
to  magnetism  proceeding  from  the  sun  ;  if  we  could 
find  the  correct  way  to  construct  on  the  earth  some- 
thing analogous  to  the  electrical  conductors  upon  the 
dynamo  armature  we  might  be  able  to  generate  force, 
either  electrical  or  something  similar.  Such  a  scheme 
would,  no  doubt,  theoretically  at  any  rate,  slow  down 
the  rate  of  rotation  of  the  earth  and  so  lengthen  the 
day,  but  it  is  probable  that  the  total  amount  of  energy 
required  by  the  whole  of  mankind  is  so  small  in  com- 
parison with  the  vast  momentum  of  the  earth  that  that 
would  never  be  appreciable.  Of  course  this  scheme  is 
only  a  piece  of  pure  imagination,  but  it  is  sufficiently 
original  and  ingenious  to  merit  a  reference. 

Another,  and  perhaps  more  likely  source  of  power,  is 
the  rays  which  are  no  doubt  being  emitted  from  our 
sun  other  than  those  which  give  light  and  heat.  There 
is  every  reason  to  believe  that  the  waves  in  the  ether 
which  convey  light  and  heat  from  the  sun  to  the  earth 
are  accompanied  by  other  waves  of  different  lengths 
from  those  which  we  perceive  with  our  senses,  and 
there  may  be  possibilities  in  some  of  these  which  we 
have  not  up  till  now  realised.  This,  however,  is  not  a 
subject  for  the  engineer  but  for  the  physicist  to  in- 

359 


Engineering  of  To-morrow 

vestigate  ;  but  should  the  latter  discover  that  there  is 
any  real  source  of  power  in  the  sun's  rays  which  we 
have  not  tapped  to  the  full  already,  the  engineer  will 
not  be  slow  in  finding  the  means  to  turn  it  to  practical 
advantage. 

The  third  "  solution  "  to  our  difficulty  is  not  really  a 
solution  at  all,  but  simply  a  means  of  putting  off  the 
evil  day.  I  mean  some  more  efficient  ways  of  utilising 
the  sources  of  energy  as  they  exist  at  present.  For 
example,  suppose  we  could  discover  some  form  of 
"  coal  battery  "  by  which  the  energy  of  coal  could  be 
converted  direct  into  electricity  with  only  a  small  loss. 
It  is  a  curious  fact  that,  while  we  can  convert  electricity 
into  heat  with  a  very  small  loss  indeed,  the  contrary 
process  is  accompanied  by  the  enormous  loss  referred 
to  in  the  beginning  of  this  chapter. 

It  is  quite  safe  to  say,  therefore,  that  one  of  the  great 
efforts  of  engineers  for  many  years  to  come  is  likely 
to  be  in  the  direction  of  devising  more  efficient  ways 
of  using  the  stores  of  energy  which  exist  in  our  coal 
deposits. 

Several  ways  of  doing  this  have  been  referred  to 
already,  such  as  the  use  of  the  waste  gases  from  the 
blast-furnaces  in  ironworks  for  heating  and  also  for 
driving  by  means  of  suitable  gas-engines.  All  forms  of 
furnace  are  now  made,  if  possible,  to  work  on  some 
sort  of  regenerative  principle  so  as  to  utilise  heat  which 
would  otherwise  be  wasted,  while  the  steam-turbine 
has  provided  in  a  remarkable  way  for  the  use  of  waste 
steam.  In  an  ordinary  steam-engine  the  full  force  of 
the  steam  cannot  be  made  use  of.  The  expansive  force 
within  the  steam  can  only  be  utilised  by  passing  it 
through  a  series  of  cylinders,  and  there  are  certain 
practical  difficulties  in  the  way  of  having  a  sufficiently 
numerous  series  of  cylinders  to  extract  it  all.  A  steam- 
turbine,  however,  can  be  arranged  so  that  practically 

360 


Engineering  of  To-morrow 

every  ounce  of  force  in  the  steam  is  transferred  to  the 
rotor  of  the  turbine,  so  that  it  comes  out  at  the  "  ex- 
haust" end  like  the  steam  from  a  lightly  boiling  kettle. 

Indeed,  the  turbine  will  go  even  farther,  and,  if  this 
exhaust  steam  be  led  through  a  turbine  to  a  condenser, 
the  waste  steam  from  an  ordinary  engine  can  be  made 
to  do  an  astonishing  amount  of  work.  In  many  cases 
a  factory  is  lighted  throughout  by  electricity  generated 
in  this  way,  by  an  exhaust  turbine  using  the  steam 
which  for  many  years  previously  was  allowed  to  run 
to  waste. 

The  steam-engine,  whether  reciprocating  or  turbine, 
however,  suffers  from  one  great  difficulty.  A  certain 
amount  of  the  heat  employed  becomes  locked  up  in 
the  steam  and  cannot  be  recovered  and  put  to  use,  but, 
on  the  other  hand,  often  requires  an  expensive  plant  to 
get  rid  of  it.  Who  has  not  noticed,  at  some  large 
generating  station,  huge  erections  of  wood  of  such  size 
that  they  are  perhaps  the  most  prominent  feature  in  an 
outside  view  of  the  station.  Those  are  cooling-towers, 
and  their  purpose  is  to  dissipate  into  the  atmosphere 
heat  which  would  be  valuable  if  it  could,  instead,  be 
captured  and  taken  back  to  the  boiler.  Heat  is  con- 
sumed in  converting  the  water  into  steam,  and,  in  order 
to  get  as  much  force  as  possible  out  of  the  steam,  it 
must  be  converted  back  into  water  before  it  is  liberated. 
This  is  done,  as  we  saw  in  a  previous  chapter,  by  con- 
densing it  through  causing  it  to  come  into  contact  with 
cold  water,  the  heat  in  the  steam  being  transferred  to 
the  water  which  thus  carries  it  away,  and  it  is  that 
water  which  has  to  be  cooled  at  considerable  expense. 
Even  in  those  cases  where  there  is  no  cooling-tower 
there  is  something  equivalent,  either  nozzles  by  which 
the  water  is  thrown  into  the  air  in  fine  spray,  or  else, 
where  there  is  a  stream  handy,  the  cold  water  is 
drawn  from  the  stream  and  the  hot  put  back.  In 


Engineering  of  To-morrow 

any  case  the  result  is  the  same,  good  heat  is  being 
wasted. 

Similar  considerations  apply  to  the  internal-com- 
bustion engine  in  its  many  forms.  Heat  which  ought 
to  be  put  to  good  use  has  to  be  got  rid  of  simply  be- 
cause up  till  now  we  have  not  found  a  satisfactory  way 
of  making  use  of  it.  Along  these  lines,  therefore,  we 
may  expect  to  see  great  developments  in  the  future. 

Another  field  for  ingenuity  and  research  is  the 
electric  accumulator.  Just  think  how  the  problem  of 
installing  electric  trams  would  be  simplified,  did  we 
but  possess  a  light  and  efficient  accumulator.  There 
would  then  be  no  need  for  the  unsightly  overhead 
wires,  or  the  costly  surface  contact  or  conduit  systems. 
Many  minds  have  been  engaged  upon  this  problem 
for  years,  including  that  of  Mr.  Edison,  but  so  far 
without  any  conspicuous  success. 

New,  simpler,  and  cheaper  processes  and  machines 
for  all  purposes  are  always  required,  and  of  these  we  shall 
without  doubt  see  many  examples  in  the  years  to  come. 
There  is  a  great  need  for  trained  scientific  men  to 
tackle  these  industrial  problems.  It  is  not  enough 
nowadays  to  go  blindly  on  in  the  hope  that  a  new 
process  or  invention  will  be  discovered  by  accident. 
The  modern  inventor  who  is  going  to  make  a  real 
success  must  find  out  something  that  is  needed,  and 
then  set  himself  patiently  and  laboriously  by  careful 
investigation  to  search  for  it.  We  shall  probably  hear 
less  in  the  future  of  the  man  who,  by  a  lucky  chance, 
invents  a  tin-opener  or  a  pencil-point  protector, 
and  makes  his  fortune  immediately,  and  more  of  the 
skilled  and  patient  investigator  who,  by  years  of  in- 
dustry, makes  an  invention  which  assists  some  important 
industry. 

The  social  reformer  (and  we  are  all  social  reformers 
to  a  degree)  will  more  and  more  need  the  engineer's 

362 


Engineering  of  To-morrow 

aid  ;  for  every  writer  who  has  attempted  to  picture 
an  ideal  state  of  society  has  found  himself  confronted 
with  the  question  :  "  Who  is  to  do  the  dirty  work  ?  "  and 
his  only  possible  answer  is  " Machinery."  The  engineer 
is  then  called  in  to  devise  wonderful  contrivances  which 
relieve  men  and  women  from  the  menial  "  degrading  " 
duties  of  life. 

The  automatic  charwoman,  the  automatic  scavenger, 
the  automatic  coal-heaver,  are  dreams  which  our 
imaginative  writers  have  dreamed  over  and  over  again, 
and  something  of  the  sort  is  not  far  off.  We  already 
have  machines  which  sweep  our  rooms,  and  peel  the 
potatoes  in  the  kitchen,  while  quite  recently  there  has 
been  put  upon  the  market  a  little  machine  humorously 
called  the  "  Electric  Mary  Ann,"  which  performs  many 
of  the  duties  of  the  general  servant — such  as  cleaning 
the  knives,  and  blacking  the  boots — with  efficiency  and 
despatch. 

In  fact,  there  is  no  class  of  men  who  will  have  a 
greater  influence  on  the  social  and  economic  progress 
of  the  world  than  the  engineers. 

In  the  introduction  I  quoted  a  remark  of  John 
Ruskin's,  which  seemed  to  belittle  the  engineer's  work. 
Let  me  conclude  with  another  quotation  from  the  same 
writer,  in  which  he  indicates  quite  the  contrary.  He 
is  discussing  the  true  principles  of  "economy"  or 
"house  management"  as  applied  to  national  affairs, 
and  he  thus  enumerates  the  great  works  which  are 
needed  for  the  nation's  happiness  and  wellbeing : 

"  The  sea  roars  against  your  harbourless  cliffs — you 
have  to  build  the  breakwater,  and  dig  the  port  of  refuge  ; 
the  unclean  pestilence  ravins  in  your  streets — you  have 
to  bring  the  full  stream  from  the  hills,  and  to  send 
the  free  winds  through  the  thoroughfare  ;  the  famine 
blanches  your  lips  and  eats  away  your  flesh — you  have 
to  dig  the  moor  and  dry  the  marsh,  to  bid  the  morass 

363 


Engineering  of  To-morrow 

give  forth  instead  of  engulphing,  and  to  wring  the  honey 
and  oil  out  of  the  rock.  These  things,  and  thousands 
such,  we  have  to  do,  and  shall  have  to  do  constantly, 
on  this  great  farm  of  ours." 

Every  one  of  these  things  is  the  work  of  the  engi- 
neer. 


364 


INDEX 


AERIAL  ropeways,  325 
Aeroplanes,  theory  of,  337 
Alternating-current  (electricity),  78 
Ampere,  the,  80 
Arc  lamp,  the,  291 
Arch,  theory  of  the,  I2O 

BALL-MILLS,  103 
Ballast  on  ships,  142 
Balloons,  346 

Bessemer  process  (steel),  95 
Bilge  keel,  155 
Biplane,  parts  of,  342 
Blackfriars  Bridge,  125 
Blast  furnace,  89,  90 
Blast  pipe  in  locomotives,  241 
Blasting  submarine  rocks,  202 
"Block  system,"  256 
Blow-pipe,  oxygen,  no 
Boiler,  Lancashire,  37 

,,       Cornish,  38 

,,      marine,  38 

,,       water-tube,  39 
Brakes,  railway,  243,  245 

„       tramway,  222 
Branca,  turbine  of,  32 
Bridge,  the  first,  119 
Buoyancy,  centre  of,  147 

CABLE-REPAIR  ship,  168 

Caisson,  126 

Cam  shaft,  51 

Cantilever  bridge,  122 

Cantilever   construction  in  theatres, 

123 

Carbon  monoxide,  53 
Carbon  in  iron,  91,  93 

,,       in  steel,  94 
Carbonic-oxide,  53 
Carburetted  water  gas,  282 
Cast  iron,  91 

Cement  from  blast  furnace  slag,  104 
Central  generating  station,  43 
Centrifugal  pumps,  168 
Charging  machine  in  steelworks,  100 


Chimney,  purpose  of,  37 
Coal,  source  of  heat  in,  24 
Coalite,  285 
Cofferdams,  62,  130 
Comparator,  307 
Compound  locomotives,  240 
Compound  steam-engine,  30 
Concrete  dams,  61,  209 

,,         mixers,  63 
Condenser,  surface,  42 

,,         evaporative,  43 
Conductors,  electric,  297 
Conduit  system  (tramways),  226 
Converters  (electric),  82 
Coolgardie  water  scheme,  209 
Cooling  towers,  42 
Copper  refining,  105 
Cradle  for  launching  ship,  156 
Crank  of  steam-engine,  27 
Crosshead  of  engine,  27 
Crucible  steel,  100 
Cruisers,  1 86 
Cupola,  91 

"  Cut-off,"  in  steam-engine,  29 
Cyclops,  the,  163 

DAM  at  McCall  Ferry,  6l 

Dams,  purpose  of,  66 

Decks  on  ships,  names  of,  143,  145 

Destroyers,  187 

Diesel  oil-engine,  58 

Direct-current  electricity,  78 

Displacement,  tonnage,  140 

Diver's  dress,  194 

Diving  bell,  199 

Dog-shores,  158 

Double-bottom  of  ships,  153 

Dredgers,  166,  167 

Dreadnought  battleships,  184,  185 

Dynamos,  77,  79 

EARLY  steam-engines,  26 
Eccentric,  28 

,,         rod,  28 

„         strap,  28 


365 


Index 


Economise!,  37 
Elasticity  of  steam,  29 
Electric  driving  in  mills,  75 
„       furnaces,  293,  295 
,,        motors,  75,  84 
Electrical  measurements,  80 

,,        refining  of  copper,  1 06 
Electricity,  what  it  is,  76 
Electro-mechanical  signalling,  270 
Expansion  of  concrete  by  heat,  66 
Explosion  of  gas,  nature  of,  46 

,,         in  gas-engine,  how  caused, 
5i»  52 

FACTOR  of  safety,  1 24 
Ferro-concrete,  329 
Filters  at  water-works,  207 
Fire  alarms,  331 
,,    engines,  333 

Flying  machines,  theory  of,  337 
Flywheel  of  steam-engine,  27 

„         function  of,  in  gas-engine, 

49 

„         how  it  stores  up  power,  99 
Forth  Bridge  distorted  by  sunshine,  25 
Foundations  under  water,  129 
Fusible  plug,  42 

GAS-DRIVEN  cargo  boat,  57 
Gas-engine,  45 

,,          how  started,  52 
Gas-pump,  59 
Gas-ships  on  the  Rhine,  57 
George  Washington,  the,  145 
Girders,  types  of,  1 21,  122 
Guns,  particulars  of  heavy  naval,  177 

HALF-SPEED  shaft,  51 

Hall  electro-gas  signals,  269 

Heat  engines,  25 

High-speed  saw,  109 

High-tension  currents  (electricity),  So, 

o2 

Horse-power,  316 

"  Humphry  "  gas-pump,  59 

Hydroplanes,  345 

INCANDESCENT  electric  lamps,  290 
Interlocking  railway  signals,  54 
Internal-combustion  engines,  45 

KEEL  blocks,  152 


LIFTS,  318 
Lightship,  171 


Limestone,  use  of  in  smelting  iron,  89 

Liquid  air,  112 

Live-rollers,  98 

"Lock  and  block"  (railway  signal- 

ling), 259 
Lots  Road  Generating  Station  (Lon- 

don), 43,  81 

MACHINE  tools,  108 
McCall  Ferry,  dam  at,  6  1 
Malleable  cast  iron,  93 
Manchester  Ship  Canal,  bridges  over, 

135 

Marine  steam-engine,  31 
Menai  Straits,  bridge  over,  151 
Meters,  311,  312,  315 
Micrometers,  305 
Mild  steel,  94 

Minas  Geraes,  the,  180,  182 
Monoplane,  parts  of,  341 
Motor  sledge,  for  the  Antarctic,  351 
Mould  -loft,  152 
Moulds  for  concrete  dam,  64 
Moulding  box,  92 

,,         machines,  93 
Mushroom  valves,  50 

Neptune,  launch  of  the,  155 
Nickel-chrome  gun  steel,  175 

OHM,  the,  80 
Oil-fuel,  141 
Ores  of  iron,  88 
Otto-cycle,  50 

PARSONS,  Hon.  C.  A.,  32 
Parsons  turbine,  32 
Pelican  crane,  64 
Pelton  wheel,  71 
Periscope,  188 
Permanent  way,  252 
Petrol-motor,  58 


Pig  iron,  91 
Piles, 


366 


how  they  are  driven,  127 
Piston  of  steam-engine,  26 

„     ,,  gas-engine,  50 

,,     rod,  26 
Platelayers,  252 
Pneumatic  tools,  113 
Portland  cement,  101 
Ports  in  engine  cylinder, 
Presses,  hydraulic,  117 
Printing  machine,  352 
Producer-gas,  53 
Propelling  ships  by  water-jet,  60 


28 


Index 


Puddling,  93 

Pumping  engines,  27 

Punching  and  shearing  machine, 


118 


QUADRUPLE -EXPANSION  steam-en- 
gine, 30 

REGENERATIVE  principle  in  furnaces, 
examples  of,  97,  103 

Renard  train,  350 

Riveters,     human,     pneumatic,     hy- 
draulic, 114,  115,  n6 

Roller-bearings,  87 

Rotary  kiln,  102 

,,       washer  in  gasworks,  280 

SAFETY-VALVE,  41 
Scrubber  in  gas  producer,  56 
Self-discharging  collier,  164 
Siemens-Martin  process  (steel),  96 
Single-phase  current,  83 

,,          ,,      railway  motors,  233 
Slag  from  blast  furnace,  87 
Slide-valve,  28 
Slurry,  102 
Soaking  pit,  98 
Softening  water,  214 
Sounding  machines,  311 
Speed  of  steam-engine,  30 
Sprinklers,  331 

"Staff-system  "  (railway),  262 
Steam  boilers,  36 
„      chest,  28 
,,      engine,  24 

,,      high-pressure,  31 
expansion  of  water  into,  26 
turbine,  action  of,  33 
defect  of,  34 
astern,  35 
,,        exhaust,  35 
„        arrangement     of    on 

ship,  35 

,,  ,,        Curtiss,  36 

,,  ,,        De  Laval,  36 

„  „         Rateau,  36 

,,  ,,        Westinghouse,  36 

Stokers,  mechanical,  40 
Submarine  boats,  188,  189 


Suction  gas  producer,  53,  54 
Superheater,  steam,  38 
Surface-contact    system    (tramways), 
226 

"TABLET-SYSTEM"  on  railways,  262 

Theodolite,  use  of,  132,  133 

"  Thermit "  welding,  227 

Three-phase  current,  83 

Tide-mills,  71,  72 

Titan  crane,  321 

Tonnage  of  ships,  139 

Tool-steel,  100 

Torpedoes,  192 

Tramway  controllers,  218 

,,        motors,  218 
Transformers  (electrical),  8l 
Transporter,  323 
Triple-expansion  engines,  30 
Trough -flooring  for  bridges,  117 
Tube-mills,  104 
Turbine-locomotive,  247 
Turbine,  steam,  33 
water,  68 
Turret-ships,  141 
Two-phase  current,  83 
Typesetting  machines,  353 

UNDERGROUND  railways  of  London, 
81 

VACUUM  brake,  243 
Valve  spindle,  28 
Vapouriser,  57 
Volt,  the,  80 

WASH  mill,  101 

Water-tight  bulkheads,  144,  146 
Water  turbine,  61 
Water-wheel,  Pel  ton,  71 
Waterloo  Bridge  (London),  120 
Westinghouse  brake,  243,  245 

,,  electro-pneumatic  sig- 

nalling, 270 

Winchester  Cathedral,  201 
Wire- wound  guns,  174 
Worthington  pumping  engine,  211 
Wrought-iron,  93 


Printed  by  BALLANTYNE,  HANSON  &  Co. 
Edinburgh  d^  London 


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